Transcription
The science of solving crimes has changed, and it's all over TV and the movies. But does Hollywood get it right? Can you really solve a murder by looking at blood spatter or a bullet found at a crime scene?
For the real CSIs, the secret is in the details, and there is no perfect crime. Every criminal leaves a trace, so get your facts straight and snap on some rubber gloves as we head to the forensics lab to discover beyond a doubt what that's about.
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Combing a crime scene for clues and turning them into evidence is guided by science. Our goal is the pursuit of scientific truth, wherever that leads. This is why the real crime-scene investigators are nothing like you see on TV. It's not instant science as people might see on television. In the real world, forensic science is a long, tedious process with checks and balances at every step. Analyzing a DNA sample takes days, not minutes. Nothing guarantees a bullet will match the gun, and blood doesn't always appear like magic.
So when forensic investigators arrive at the scene of a crime, there is no rush. They know their every move goes on record and that the margin of error is zero.
On certain TV shows, crime scene investigators seem to do it all. They interview suspects and analyze clues, but that's not what real CSIs do. Senior investigator John Kerry and his team do one thing and one thing only: they are very specialized. Their job is specifically dealing with the evidence going into the scene and collecting the evidence.
The work John and his crew perform creates the basis of the entire investigation. If they smudge a fingerprint, don't perfectly follow procedure, or contaminate the scene, the whole investigation can be thrown out of court, and a criminal could walk free.
Thanks to TV, crime scene investigators have to deal with what they call the "CSI effect" when they testify in front of jurors. If it doesn't match up with what somebody saw on a television program, which they now believe to be the way to conduct it, they may feel that we did not do our job.
Another reality that rarely makes it into TV dramas is the mountains of research forensic teams rely on to do their jobs. In a murder investigation, for example, it's essential that investigators determine the time of death. They can use the stiffness of the body or its temperature as indicators, but only if the body is found relatively soon after death. Past that, you need the expertise of Dr. Neal Haskell, one of the world's leading forensic entomologists.
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He uses bugs found in corpses to determine the time of death. That's what forensic entomology is all about. What we're looking for on the insects that we find on dead bodies—on corpses—are primarily the life stages of certain flies and beetles that will help us primarily determine time of death. Bugs eat corpses, so the older the bugs, the longer the body has been lying there.
Once Dr. Haskell determines a maggot's age, he can work backwards and establish the time of death. Dr. Haskell finds all sorts of different insects on corpses, but the holy grail of forensic entomology is the blowfly.
"I love them. These are my girls. The food source is specific. They don't go to fecal material; they don't go to garbage. They go primarily to rotting meat or initially fresh meat that becomes rotten over a period of time."
Dr. Haskell uses the blowfly because its lifecycle runs like clockwork. When a blowfly lays eggs, they'll transform into maggots within the first day. As a maggot feeds on the corpse and gets bigger, it sheds its outer skin. The maggot will grow a hard shell and transform into a pupa while safely inside. Depending on the species and the temperature, the adult blowfly emerges a few days later.
If Dr. Haskell can determine the age of a fly plucked from a corpse, he'll be able to estimate the body's time of death.
"Gut tract ready to go!"
I'm driving. Dr. Haskell and his two assistants are on their way to pick up today's test subject: a 100-pound dead pig.
"We're gonna go get some dead pigs. Does it stink? You guys can have the head, and I'll take the butt."
The carcass is brought to Dr. Haskell's own research facility in Upstate Indiana. As the pig decomposes, they will study the evolution of the blowflies growing on it.
"The reason we're using pigs in our experiments is that we found that the pigs will approximate the human decomposition almost identically with regards to the insects that they attract. Maybe by this evening, we'll have maggots. At least by tomorrow morning, we'll have maggots—little teeny tiny ones—but there'll be maggots."
"I'm hungry. Dinner is served for the maggots."
Maggots just feed voraciously, and that's why we talk about the maggot sounds. It sounds like the biggest bowl of Rice Krispies you ever heard: snap, crackle, pop.
"Okay, well, let's go that way."
After lunch, Dr. Haskell and his assistants return to the field.
"We're heading back to the circle of death, as we call it, back in the woods where we are to collect some specimens regarding larval specimens and some adult specimens so that Matt can have his adult female flies to lay eggs so we can do some testing on growth development."
"Nice to be this far away from the house; that way we won't smell it."
"We need the maggot motels."
"I'll get this."
When the pig first starts to decompose, internal gases are released through its nose, mouth, and butt. The smell is a magnet for blowflies. The blowfly females are so sensitive that you and I can be standing next to a dead pig or a dead human, and we can't even smell them. Yet this female blowfly can smell it from a mile and a half to two miles away.
This pig's body has only been under the sun for three hours, but thousands of eggs have already been laid on it. There are over 90 species of blowflies in North America, and they all live in different regions. That can be handy. If we have a Rocky Mountain species on a body here in Indiana, I'm gonna go, "Excuse me, but I think we might want to look further west and see if we can find the right location."
"Go pick some maggots."
"It looks like there are tons of maggots."
The speed at which the blowfly maggots can flesh a body is really amazing. We have records of some of our research in the early '80s of where we had a pig of 50 pounds. Within 96 hours, it's down to 18 pounds. Worldwide, there are 1,100 different species of blowflies, and they all mature at different rates.
To establish an accurate time of death, Haskell has to keep the maggots alive to identify the species.
"This is a maggot motel, and this is where the maggots will live. We're making the maggot pouches where we put the live maggots and the food source into these women floor pouches to help maintain the moisture for the maggots too, so that the food source doesn't dry out. It also maintains the integrity of their confine so that they aren't wandering all over; they're staying right on the food."
Dr. Haskell and his assistants head back to the lab with the maggots. Only adult flies can be identified by species, so they'll wait for the maggots to hatch into flies.
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That's the only way they'll be able to put them under a microscope to identify the species. This is a job that comes down to the smallest of details. Whether a hair is present or absent will separate one species from another. Whether a hair converges or diverges will separate species.
Dr. Haskell needs to know what species he's working with because their life cycles vary. The weather also plays a big factor. As it cools down, their growth or development slows. As it warms up, their growth or development occurs faster and faster.
If the body has been exposed for days, Dr. Haskell will then work with hourly temperatures. If it's months, he has to go by a day rate. The longer the body has been out, the less precise his time of death can be.
But the new frontier for forensic entomology is DNA. These flies fed on the victim's body, which means that the victim's blood can be recovered from the insect's digestive tract. With modern DNA technology, even a sample this small could be used for identification and for toxicological analysis.
If you look at a maggot closely, you'll see a little dark speck, a red speck towards its head. That's the crop. As they ingest their meal, they'll take the meal in and store it in that crop before it's passed on to their digestive system. While it's in that form, there are elements of human DNA from maggots that have been feeding on a body.
When the body has been removed and only the maggots are left behind, we might be able to get the victim's DNA from those maggots.
Forensic experts always come too late; it's the nature of the job. But the work they perform helps solve crimes.
"If I can help get a conviction on a person and make sure that that never happens again, the contribution is tremendous."
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Some call it the Anthropological Research Facility at the University of Tennessee at Knoxville; others just call it the body farm. Their business is the study of human decomposition, and they don't use pigs—they use actual donated human bodies.
One of the experts here is Rebecca Wilson.
"The focus to us is what is happening to the body. We will look at color changes; we will look at the appearance of skeletal elements, presence of hair masses. We've studied sun versus shade, indoor versus outdoor, being in a car, being in a garbage bin—looking at all those things and how it would change that decomposition."
Since the body farm opened in 1972, over 300 corpses have been left on these acres. Most remain until they've decayed completely, leaving only bone. Prior to this establishment, there was no way to actually investigate in a scientific manner the time since death or what occurred to a body in any variable after the person dies.
By documenting the process and rates of decay, this facility has given investigators an invaluable tool. The body farm has two main research projects currently operating. Rebecca is participating in both studies.
The first is about collecting DNA in the hopes of discovering how far into the decomposition process a viable DNA sample can be retrieved. Tissue samples are collected once a week, and then we actually take bone samples as well in the beginning and end of decomposition.
They are also studying how garbage dumpsters affect decomposition rates. Rebecca is replicating a grisly reality inside this 70-gallon dumpster: our decomposing human remains.
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The longer the body decays, the harder it becomes to give a precise time of death. But thanks to this kind of research, crime-scene investigators can narrow it down.
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The science of decomposition would not exist if it weren't for the people who've donated their bodies.
"Most of our donations are usually educators or people in the medical field. We get a lot of nurses and a lot of teachers. They receive an average of 30 to 50 bodies a year, and each one serves science somewhere on the body farm."
Most donations are out here for usually six months to a year; that's roughly the time it takes for the soft tissue to decompose.
"We're here to look at ways to improve the recovery on actual forensic scenes. So you want to see what animals do; you want to see how things naturally move. That's why we leave them out here."
She needs the help of a GPS unit to locate all these buried and semi-buried bodies. Samples from the DNA study are taken weekly until there's nothing but bone.
"It looks like I got everything I can pick up for the time being."
Once the individual becomes skeletonized out here, we actually pick up the donation.
"These are just your hand bones, but I also was able to pick up part of your vertebra. This is in your spinal column, so it's a much larger element that you don't want to miss. But you get a lot of hands and feet; we do recover a lot of fingernails."
Once every piece is recovered, it's brought inside the facility where every single bone gets numbered, measured, and catalogued. The Anthropological Research Facility has one of the largest collections of non-archaeological skeletons in the U.S.
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"It's like a library of skeletons. By comparing the bones of people from different genders, age groups, and ethnic backgrounds, patterns emerge. This allows for research looking at the biological profile that's used for identification of missing persons."
"So we can look at aging a skeleton, the sex estimation of a skeleton by what they did for their life occupation. We can help with all aspects of identifying a missing or unidentified person."
On TV, you get instant results moments after the CSIs hit the crime scene. They get fingerprints, a murder weapon, and a time of death. But in a real-life case, these things take time, especially if forensic scientists have nothing to work with but bones.
When the only evidence is skeletal, detectives turn to the C.A.P. Human Identification Laboratory in Gainesville, Florida. The expert here is Dr. Anthony Falsetti. He has cracked cases for the United States Army and the FBI. He helps the dead speak.
"By the time we get a case, generally the tissue and the organs are no longer available for any meaningful study, and that's why the cases get turned over to this lab. Our expertise is in hard tissue: bones and teeth."
Every case is unique, but with each set of remains Dr. Falsetti receives, he asks the same two questions: try to determine who the individual was and what happened to them. To do that, you need a body—or at least part of it.
Today, Dr. Falsetti signs for a very special delivery. Inside this cooler is a human skull. He'll try to determine the victim's identity and what happened to him using only the skull.
"So we just got this case. There's a suspicion of blunt-force trauma. I'll take a quick look at it and then go ahead and take an x-ray of it."
The x-ray confirms the detective's theory: this man was hit hard on the head—so hard it cracked his skull. But not all cases are that obvious.
"We may only have half of a body, and those are always real challenges. The others that are really challenging are when we have no idea what happened to them. Either there's no evidence of injury, or there's nothing obvious."
Dr. Falsetti works with unidentified bodies that have decomposed to the point where there's nothing left but bones. If small amounts of flesh remain, he has to remove them before beginning his analysis.
"This is done carefully with scalpel and brushes. It's a matter of removing that soft tissue."
Here in the lab, they will use plastic tools so they don't leave any additional injuries. But no handheld tools are delicate enough to remove trace amounts of tissue, which is where the ghoulishly named maceration tank comes into play.
"It's a process called water maceration, and you simply put the body in a very large vat of water, let it heat up, and eventually that soft tissue will boil away. After 24 hours, there's nothing but bone."
The bones are dried, laid out, and measured. At this stage, a lot of information can be confirmed or refuted. For example, the skeleton of a person that does manual work outdoors is very different from that of an office worker.
Dr. Falsetti can tell them apart. He can also track injuries, even if they happened in childhood. Injuries leave a bone scar. Each millimeter of every bone is examined with a microscope.
DNA can also be collected from bones. Dr. Falsetti's methods can solve mysteries even for decades after the fact.
"We resolved a case from 1967, and that was really neat because the family—this was a young man at the time—and his sister is still alive. She's in her late 70s, and we, working with our DNA folks here, finally made a DNA match. Law enforcement was able to tell her they finally identified her brother. He had been sitting in a box in our lab since 1974."
If you thought scraping flesh from bone and then boiling the skull was grisly, you haven't seen anything yet. What does Dr. Falsetti consider the most horrifying aspect of his job?
"Paperwork."
You don't see much of it on TV, and that's not the only reality check.
"We could never resolve something in 40 minutes. We have a nine-year-old Chevy Astro van; we don't have Hummers. So what we actually do, you know, can entertain people when it's certainly influenced, if not this generation, the next generation of young scientists."
No sports cars, no guns, and no instant lab results.
So what does Hollywood get right? There is one thing, and it's the most important: on TV and in real life, forensic teams work to discover the truth so justice can be served.
"When someone is deceased, there's nothing we can do for them except try and see that some form of justice is done. We do that by making sure we don't mess up the crime scene, making sure that the evidence is collected properly, and that we're able to work with the other entities and get a conviction."
Thanks to research and the skills of CSIs like John Kerry and his team, the smallest detail found at a crime scene can be used to put criminals behind bars. But only if the forensic scientists can turn these clues into evidence, and that's done at the lab.
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In New York, the lab is at the Forensic Investigation Center in Albany. It's one of the largest forensic centers in North America. Inside, 240 scientists specialize in dozens of different kinds of forensic analysis: biological science and DNA, fingerprints, drug chemistry, trace evidence, ballistics, and of course, an autopsy room.
The building has over a hundred thousand square feet, cost almost twenty-five million dollars to build, and is entirely devoted to forensic science. Major Rich Nutso runs the facility, which has been nicknamed "the house the crack built."
During the seizures of large amounts of cocaine and these kinds of drug arrests, those assets would be turned over to criminal justice agencies that participated in the arrest. Some of that money was set aside over a number of years to fund this construction.
When the CSIs come in from the field, their first stop is here at Roger Williams' desk.
"When it arrives here, it's checked to make sure that all the seals are intact, that it's properly packaged, that it's dated and initialed, and that it's going to be preserved. Once we put it into our vault against any type of loss or contamination, establishing whose hands the evidence is passed through is key to convincing jurors it has not been tampered with."
The vault is four stories high, which is good since 100,000 new pieces of evidence have to be stored in it every year. Not one piece of it goes in or out without an evidence receiving clerk documenting its travels.
After the evidence is bagged and tagged with a barcode, the receiving clerk takes it straight to the evidence vault—a place off-limits to everybody. Not even scientists are allowed here.
"You just can't walk around in here, and like you see on TV where people are just walking around the lab. This is a very restricted area."
Unlike on TV, once CSIs submit the evidence, their work is done. They won't know if the evidence has the power to convict until the results come back from the lab.
When guns are found at a crime scene, they're turned over to James Campbell. He's a technical sergeant in the firearms identification unit at the New York Forensics Investigation Center.
If a gun is used in a crime, forensic investigators have a few ways of tracking its owner. But even if they don't have a gun, the bullets will do.
"When a bullet is fired down the barrel, any markings that are on the inside of the barrel are transferred in mirror-image to the bullet. That's the thing we look for: these markings are striation marks."
When manufacturers make pistols, rifles, or revolvers, they cut a series of grooves into the hard steel barrel. These grooves spin the bullet as it comes out of the barrel, ensuring it flies in a straight line. With wear and tear, the marks become the fingerprint of a gun; no two are the same.
Another set of marks is created when the firing pin strikes the rear of the cartridge case. The impact leaves marks on the primer and sometimes on the rim of the case. Breech marks are created when the cartridge slams against the back of the weapon, imprinting microscopic marks on the casing after the gun is fired.
All that's left of the bullet is its case. Extractor and ejector marks are sometimes found on it; they're produced when the case pops out of the chamber.
"To check for marks, the identification unit runs a test-fire. You have to look at the test-fire to make sure that there is a repeatable pattern that's being produced by the weapon, either with the cartridge casings or the projectiles that come out of the barrel as well."
You'd think a bullet would shoot straight through this tank, but the friction from the water is enough to slow this bullet down. What might have gone a mile through the air doesn't even get halfway down this tank.
The bullet is recovered from the water and analyzed through a comparison microscope. Here, two objects can be viewed simultaneously. On the left is the bullet recovered at the crime scene; on the right, the bullet from the test-firing.
"Right now, I'm looking at the breach marks that were put onto the casings by the gun, trying to compare them—the test-fires to the evidence from the crime scene."
Another way to identify a gun is with its serial number, and that's why some criminals work hard to erase this identifier.
"The top gun is a gun from a crime scene. The defendant has defaced the serial number. The bottom gun is one of our reference collection guns that we keep here in order to see what these serial numbers look like."
Right now, the serial number is impossible to read, but Jim has a few tricks up his sleeve.
"The process first is to polish the surface of the area where the serial number was in order to get an even surface. Then we take some weak acids that are called chemical etchants and we etch the area around where the number was stamped in order to bring back the number or raise it as it appears to produce a trace image of the original stamp."
All it takes is a Q-tip and a 20% nitric acid solution. The nitric acid produces a chemical reaction with the metal of the gun. It's like rubbing a pencil on a piece of paper to see what was written on the page above it.
It could take a number of hours in order to get the full serial number back. It depends on the way the numbers were taken off. When the serial number is stamped onto a gun, the metal underneath gets compressed and hardened. So even if the top layer of metal is removed, traces of the impression may still be present below.
Retrieving a serial number is not foolproof. In some cases, like this one, the remaining traces are not legible.
"It's a process that sometimes can be lengthy and sometimes is not as fruitful as we'd like. But one negative result won't stop the scientists. They know the criminal left a clue; they just need to find it."
When guns are used in homicides, the fatal impact usually produces blood spatter patterns. In these cases, the evidence is literally written in blood, and the man who knows how to read it is Lieutenant Steve Cohen in Lafayette, Indiana.
"Steve studies the blood patterns left behind at crime scenes to give detectives a picture of what happened. If he can discover how the spatters were made, Steve can help determine how the crime was committed."
For demonstration purposes, he usually uses animal blood since it doesn't carry human pathogens. But if the case is going to trial, only the real thing will do. To make sure juries have no doubts about his research, Steve prefers to use human blood—his own blood.
Blood spatter patterns come in two main types: projected spatter and passive spatter. Stains can also be caused by transfer.
Projected spatter results when a force hits a blood source. This can be low-velocity impact, like a splash from a puddle, or medium-velocity impact, like a hit from a baseball bat.
"The head is a very blood-rich environment, and once blood starts to flow, if it's impacted, you get this type of a violent reaction. A gunshot wound produces an even more violent spatter. This pattern is categorized as a high-velocity impact spatter."
Passive spatter is what's caused naturally—blood dripping down from a wound, flowing away, and pooling on the ground. It's a good indication that somebody stood in one spot and bled.
"Was this the suspect's blood? Whenever we find passive blood at a scene, we become very interested in it because a lot of times, especially in a knifing situation, the suspect will cut himself on his own knife, and we can collect that and compare his DNA to it."
Blood patterns also result from transfer when blood travels from one surface to another, such as fingerprints, a blood swipe on clothing, or an arm, or something as they're moving through a hallway or something that's thrown that has blood on it.
To find out where the victim was situated when the crime was committed, Steve calculates the trajectory of the spatter.
On TV, they use laser beams, but lasers are hard to photograph, so Steve prefers using string.
"It's just as accurate. You first throw a line through the long axis of the stain and extend that out. You do that to a number of six to seven well-developed stains and see where those lines intersect. That gives you the point of convergence."
It is important for an investigator to know whether the individual was standing up, sitting down, or laying on the floor when he was attacked.
"When the actual event, the impact, occurred to the individual, this information can sustain or refute a suspect's version of events."
But even if blood is invisible to the naked eye, Steve doesn't give up.
"If there is blood present, it will show."
So by illuminating a soft blue light, he's spraying luminol. It causes a chemical reaction with the iron found in blood and produces glowing results.
Jobs don't get much dirtier than this, but Steve likes the challenge.
"I got involved in this profession to make sure that people did not get away with crimes, and yes, that's my ultimate goal."
Every crime scene is unique, but they all have one thing in common: they might hold the clues that will solve the crime. Turning these clues into convictions is the job of the forensic investigator.
The most extraordinary tool CSIs have to fight crime today is called DNA. DNA is a genetic fingerprint; it can be recovered from biological material like blood, saliva, hair, or skin.
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Dr. Barry Dushman is the director of biological science at the Forensic Investigation Center in Albany, New York. DNA is the name of his game.
"We've got tens of trillions of cells in your body, and every one of them has a copy of the DNA, so it's very hard to evade DNA evidence. But what gets done with the flick of a switch on TV is actually a complicated process."
The first step is to extract and prepare the DNA sample. These samples are then put in a thermo cycler. This machine produces multiple copies of the sequence. Finally, an image like this is produced so the system can then interpret the DNA code. This is what allows scientists to make an ID match.
This DNA lab is one of the biggest in the world, with more than a hundred staff members who process over 50,000 samples each year. Law enforcement has embraced the technology; they like DNA technology, and they like to use it, so they're always inventing new applications for us—new classes of crimes.
Producing the data is a repetitive task requiring multiple samples—a chore better suited to robots than to people.
"We would never be able to hire enough humans basically to satisfy the need. The machines can analyze up to 1,000 genetic sequences a day."
But robots can't do everything. Looking at every inch of a piece of evidence to find semen needs a human eye and a human mind.
"If she sees something that looks like a stain, she wanted to sort of—and she'll do another chemical test. Okay, in this case, you're probably looking for the presence of semen."
On TV, the hard work of securing DNA evidence, processing the sample, and matching it with a suspect is compressed into minutes. But in reality, it's not so easy.
"We can't get the DNA test done within an hour with commercials. The fact is it takes us several days to do a DNA test right now."
And while police forces around the world are collecting DNA information and building fast databases, they don't have a file for every ordinary citizen, like some television programs would have us believe.
"What we can do is we take that DNA pattern from the evidence, sit down at the computer, and run it against our database of convicted offenders and see if that pattern matches."
The amount of biological material needed to get a DNA pattern is constantly getting smaller, partly because of this thing: it's a fast excimer gas laser, and it's about to change the science of trace analysis forever.
This piece of equipment is cutting-edge—one of only a handful in the world—and Dr. Frank Padula operates it.
"In the past, cold cases may not have been solved because they might not have found biologic material on a substance. Now, with the laser, we'll be able to extract this from a minute amount."
The fast excimer gas laser can identify substances with only molecules to work with.
"We're not just talking parts per billion, but parts per trillion. That's roughly the concentration of ten drops of ink in an Olympic-sized swimming pool. We're calibrated at five parts per trillion, so our detection limit is very, very small. Our sample would need to be like the speck of a glass or a fiber—just the size of a head of a needle—and that's more than enough sample."
First, Dr. Padula takes a sample of evidence, like this piece of glass. He puts it on this laser cell under a microscope.
"This laser beam can be as thin as five micrometers. It's so precise and focused; it works like a molecular knife, cutting the bonds between individual molecules. There's no heat, so there's no damage to the original piece of evidence. It's just a pure, clean-cut sample ready for analysis."
The expert is similar to LASIK eye surgery; this is just more focused and more powerful.
"Obviously, if I'm gonna laser a piece of glass, I'm not laser-blading tissue."
But there's a price to pay—a big one. The fast excimer laser costs up to half a million dollars.
"But according to Dr. Padula, that's a small price to pay to find a rapist for your daughter. How much do you want to put a price on that? Where you thought there was not a rape, the excimer could find a rape. So now, how much does that work to you? Is that worth a hundred thousand dollars?"
Somewhere in this crime scene is the evidence that will put the perpetrators behind bars.
Fusing science with detective work, forensic scientists have revolutionized the way criminals are caught and convicted. Their work would be impossible without computers.
Unfortunately, the good guys aren't the only people with state-of-the-art technology. The problem is that criminals are going high-tech as well, which is why the Forensics Investigation Center in Albany, New York, has an entire lab devoted to computer crime.
The man in charge of it is Terry Alban.
"There are reams and reams of data in a computer. It's comparable to looking at a tractor-trailer load of paper. That's a lot of evidence inside one little box."
So when computers are seized from a crime scene, they're treated with extra care.
"The first thing they do is pull out the hard drive. This is where most of the data inside the computer is stored. To ensure evidence doesn't get lost, a complete copy of the hard drive is made. But to make sure the evidence is not contaminated, the suspect's drive is first hooked up to a write blocker so no additional data is written to it."
"When we're done, we essentially have three copies of that drive: we have the original drive, we have the copy that's saved on our server, and then we have a copy that we archive to CD so that we can bring that case back in and open it back up to look for additional evidence."
But wouldn't even the dumbest criminal know enough to simply delete anything incriminating?
"Well, the truth is that simply deleting a file doesn't remove it from your hard drive. In most cases, the data associated with that file is still on the system, and it takes a little bit of work from us, but we can carve that data back out into the file that was there and present that deleted file in its original context."
"We may even be able to present dates and times that the file was created on the system, that the file was modified or accessed. So deleting a file doesn't really get rid of the data that's associated with the file; it just removes the pointer to that data."
This means that the emails a suspect sent, the documents he's written, and the websites he's visited are still on that hard drive. Terry Alban just has to find them.
The first hurdle is cracking the password, which they don't even need technology to do.
"It relies on the field investigator to do a good interview to get passwords—to find out pets' names and kids' names and stuff like that, because that's typically a lot of times what people will use as passwords."
But criminals still have ways of covering their digital tracks. One way of hiding potentially incriminating evidence is called steganography.
"In the computer age, this means hiding a piece of information within digital files. Evidence criminals don't want investigators to find is intentionally mixed up with other pieces of data."
Now, the image on the left is the original; you can see it's clear. If you look at the image on the right, where my cursor is, you see some pink and green and a little blue. So within that image, a secret message is hidden.
"It does that by simply changing some of the bits and bytes within that data to hide this image. With steganography, you simply have a file, and unless you know that it has been altered, it's very hard to determine that there's a message hidden within that file."
Another method criminals use to keep evidence from the hands of investigators is called encryption.
"Unlike steganography, where the message is actually hidden, when you use encryption, the message is not hidden; it's just converted into a format that is not easily readable. Forensic investigators must break the code if they're going to get the evidence to court."
But Terry often always gets his data.
"Criminals might be careless, but their crimes are getting more sophisticated, which is why the forensic team has to keep ahead of the bad guys."
In Albany, New York, John follows procedures, Steve runs more experiments, Dr. Haskell pins one more blowfly, Rebecca receives a new long-term guest, Jim gets another match, and Frank scores a DNA sample.
At the forensics lab, science will always be one step ahead of crime, and that's what that's about.
[Music]