Along with human DNA evidence, DNA markers are also found in plants and animals. When Shirley Duguay was reported missing, police found her car abandoned in a field with blood spattered on the windows. Police searched the area and found a bag that contained a bloody jacket and a pair of men’s shoes. On the jacket, police found white cat hairs. Forensic tests proved that the cat hairs came from the suspect’s cat, Snowball. It was the first time animal DNA testing had ever been done and the first time it was ever used to convict someone of a crime (HBO Autopsy 4)
In a murder case in Arizona, seed pods from a tree were found in the suspect’s truck. The seed pods looked similar to ones that grew on a tree in a remote wooded area. The murdered woman’s body was found lying beneath this particular tree. A molecular geneticist was able to prove through non-human DNA testing that the pods found in the truck came from the same tree. That proved that the suspect’s truck had been at the crime scene and had brushed against the branch of the tree, causing the pods to fall into the bed of his truck. This breakthrough resulted in the first conviction based on plant DNA (Forensic Files).
Even bodies of water have their own “fingerprints.” Two boys were attacked while fishing in a pond. Three local teenage thugs had been seen in the area around the time of the attacks. When questioned, the three teenage suspects denied any involvement and claimed they had never been at the pond. Police found a pair of muddy sneakers in the home of one of the suspects. The boy claimed he had gotten mud on his shoes by jumping in mud puddles. Skeptical, police took the shoes to be tested. Scientists located a number of diatoms, microscopic creatures that live in water, on the shoes. There are many species of diatoms, but not all species live in all bodies of water. That means that there are distinguishable combinations of different species in different concentrations that are unique to each body of water. In comparing the diatoms on the shoes with a sample of water from the pond, scientists were able to conclude that the mud on the shoes could not have come from any other source. This resulted in convictions for all three suspects (Forensic Files).
There are other important areas of forensic science that are just as valuable as DNA, and sometimes the only hope investigators have of solving crimes. Trace evidence analysis is one of these areas. Trace evidence analysis uses trace evidence, usually hair and fibers, to tell a story about what occurred at a crime scene. Trace evidence is “material deposited at a crime scene that can only be detected through a deliberate processing procedure. Any individual entering any environment will deposit traces of his or her presence, and this material can be used as evidence” (Court TV). Fiber and hair comparison analysis is the process that identifies the source of hair and fibers found on a victim or at the crime scene. Carpet fibers, dog hairs, human hairs, paint particles, glass particles, dirt, and even chewed gum are always looked at as possible clues and are collected for analysis.
Hair analysis can tell examiners if the hair came from a human or an animal. When experts examine a human hair, they can identify what area of the body it came from and the race of the person it came from. Experts can also identify characteristics that indicate if the hair has been cut, colored, permed, bleached, burned, or crushed. The root is examined to determine if the hair fell out or if it was forcibly removed. If only a few hairs were found at a crime scene, investigators can start by learning if the source of the hairs was the victim, or if they are foreign hairs. If they are pubic hairs, police can assume a sexual assault took place, especially if they were forcibly removed. And at least they would know the race of the suspect that they are looking for. If a suspect is found, then the hair can be used as a source of DNA to compare to the suspect’s DNA.
Blood spatter analysis and crime scene reconstruction are other areas of forensic science that are highly valuable in piecing together evidence to determine how an assault occurred. In cases of suicide, investigators have an added burden of trying to prove whether or not the deceased took his/her own life. Blood spatter analysis tells police where the assailant and the victim were positioned, at what angle the blows or gunshots were delivered and the relative force used in the attack. The location and direction of blood spatter can help to prove or disprove any claims that a suicide took place. In many cases in which the cause of death is a gunshot wound, this is easier to prove. Crime scene reconstruction involves piecing together all of the evidence to determine the sequence of events-the nature of the attack, the location of the attack, the position of victim and offender, the time of occurrence, and type of weapon used.
Gunshot residue analysis studies the patterns and locations of gunshot residue that is always present after a gun is fired. The person holding the gun will get gunpowder on his/her hands. Blowback usually causes gunpowder residue to land on the clothing of the person shooting the gun. In one case, a woman claimed that she was asleep in a separate room when her husband was shot and killed by an intruder. When police found her nightgown by the bed that her husband was killed in, she said she left it there earlier in the evening after having sex with him. The nightgown tested positive for gunpowder residue. The reason that is significant is because of the location of the gunpowder residue on the gown. It was all on the front. That told investigators that she was wearing that nightgown when she pulled the trigger (Forensic Files).
Ballistics is another area of forensics that is dedicated to the study of guns. Ballistics experts can determine how close a gun was to the body when it was fired, if the person was shot from the front or back, and the path that the bullet traveled from the time it was fired until the time it became embedded in a person or object. This “mapping” process can pinpoint the exact location and position the victim was in when shot. Experts can also determine if a bullet (retrieved from a shooting victim) matches a suspect’s gun.
It seems that most everything has its own “fingerprint” for scientists. Even tires on a vehicle and shoes that leave prints at a crime scene can be positively matched. If found soon enough, a tire can be positively matched to a tire track left at a crime scene. Every tire is unique because of its levels and points of wear. There are also unique tiny nicks and dents in tires caused by rocks, glass, and other hard objects that can come in contact with tires. Tire impression experts can find even the tiniest clues in the rubber grooves.
The same can be said about shoeprints. Every person is unique and so are his shoes. Shoes can all start out almost the same when leaving the factory, but once they are walked in they start to develop wear patterns. Wear patterns are based on the pressure put on the shoe by a person’s weight, the unique shape of his feet and toes, the angle at which he steps, and the unique way he walks. There are also the same sort of tiny nicks and dents in shoes that are found in tires. By the same method used on tires, a shoe can be positively matched to a shoeprint.
Another “print” unique to every human, aside from fingerprints, is his/her teeth prints. These are also referred to as bite-mark impressions. Something as dismissible or often overlooked as a piece of chewed up gum, can be as damning a piece of evidence as a smoking gun. Forensic odontology (dentistry) includes not only the use of dental records to identify remains, but also uses bite mark patterns to identify suspects. Bite mark impressions can be positively matched to a suspect by making a mold of the suspect’s teeth and matching it to a bite mark pattern left on a victim’s body and even to a piece of chewed gum.
In many cases, establishing time of death can be the most important goal when looking to convict a killer. The accuracy of this determination can make it possible to identify and eliminate suspects. A good example would be the case of a man who called 911 and reported that his wife had accidentally shot herself in the head while playing with her gun. He indicated that he called 911 within minutes of the incident. Upon examination of the body, however, police were able to determine that the woman had been dead for several hours. The first indicator was the fact that rigor mortis had set in. Rigor mortis generally sets in within 3 hours of death and lasts for 36 hours. Another obvious sign to look for would be the body’s temperature. Body temperature drops around 8-12 hours after death (algor mortis) and will feel cool to the touch (Staerkeby). In more prolonged cases, where a body is in advanced stages of decomposition, the body itself yields fewer clues than do the maggots and flies found on the body.
Entomologists are the forensic scientists that study the aging process of flies, their eggs, and larvae. Coordinating these findings to the temperature that the body was exposed to, entomologists can tell how long it has been since the first flies laid eggs on the body. As soon as 10 minutes after a body dies, it begins to let off an odor that triggers a very specific and predictable pattern of insect activity. In cases where bodies are exposed, flies will find the bodies and begin laying eggs as soon as 30 minutes after death. Normally the blowfly finds the body first, and begins occupying it. Other species follow as decomposition progresses (Tenenbaum). In cases involving bodies left in enclosed spaces, the time it takes for blowflies to find a way in is also taken into consideration. It is a complex and broad science, but the information provided by insects speaks volumes about what happened to the dead when the dead can’t speak.
Forensic science is also advancing in terms of technology. In this computerized era, much of the work done in the crime labs is aided by computers. In some cases, the computers solve the crimes altogether. One such case was that of serial killer Maury Troy Travis. He made the mistake of sending a computer generated map to a local newspaper that led to his 7th victim. Feeling the need to claim credit for his crimes and to antagonize the police, he sent a note to the newspaper in response to an article they printed about one of his previous victims. The note was accompanied by the notorious map with which he indicated that they could use to locate his 7th victim. The map was downloaded from a Yahoo website. Police were able to find the killer by his IP address. This is an Internet Provider address that is assigned to individual computers when they sign on to the Internet. This address led investigators straight to the killer. In his home, they found more evidence including videos that he took of some of the murders. He was believed to be responsible for 17 murders, but some of his victims have never been found. Unfortunately, he committed suicide in jail just days after being arrested (Suhr).
Videos are also great storytellers. Videos capture bank robberies, assaults, murders, abductions, police traffic stops, just to name a few. Unfortunately, these videos are sometimes not of high enough quality to be used for positive identification of suspects. Computer forensics and digital video enhancement help to get past some of these problems. Experts can now enhance surveillance videos in various ways in order to see clearly what occurred and to get a better view of the suspects. Computer animation is another tool for crime solvers. It’s not used so much to solve a crime, but to recreate a crime. This helps to prove or disprove accounts of eyewitnesses or even suspects. It demonstrates how a crime took place, the physical possibilities, and in some cases--impossibilities. In the courtroom, forensic animation helps to give jurors a clear picture of how an event took place. By recreating a crime or an accident, prosecutors can show jurors exactly how it happened so that they can understand and see for themselves. It is considered visual aid in an investigation and helps to strengthen theories about how a crime took place. Crime scene reconstruction can bring the entire act back to life for the investigators and piece together what happened and how it happened.
It may be too optimistic to hope for world peace, but forensic science is helping to form the most effective crime deterrents ever. In this day and age, getting away with murder is no longer a feasible expectation for killers. Although criminals are getting savvier by learning about forensic methods, investigators are always a few steps ahead. If forensics continues to advance at the rate that we have seen in the past 20 years, it is a realistic hope that crime will drop drastically over the next few decades. It is certain that criminals will think twice before committing a crime if they are sure they will be brought to justice. The more cases that are made known to the public, the more criminals will find it discouraging to try to commit crimes. Letting the public know about the uses of forensic science to solve crimes, and the rate of success, is like sending a message to criminals—“whatever the crime, whatever the clues, forensics can solve it”.
WORKS CITED LIST
Forensic Files. Med Star Television. Court TV Website. August 31, 2003. <>
“Lasting Impression”. Forensic Files. Med Star Television. Court TV. July 27, 2003.
“Snowball”. Autopsy 4. Home Box Office, Inc. HBO Documentaries. August 2, 2003.
Staerkeby, Morten. “What Happens After Death?”.Department of Biology, Univeristy of Oslo, Norway. May 15, 2004. <http://folk.uio.no/mostarke/forens_ent/afterdeath.shtml>
Suhr, Jim. “Cyber Sleuthing snares suspected serial killer”. The Kansas City Star website. June 13, 2002. <>
Tenenbaum, David. “Flies in the Face of Reality”. The Why Files website. National Institute for Science Education. July 29, 2003. <>
Wells, Mike “Bodies of Evidence, What is DNA?”. Southeast Missourian website. April 6, 2003. <>
Willing, Richard “DNA’s success in crime fighting spread unevenly”. USA Today. October 6, 2002. 1A.