By Dick Warrington
This article originally appeared in Forensic Magazine® Jan. 2007, Reprinted with Permission.
The field of crime scene investigation is constantly changing. With advances in technology and science, we have more tools than ever to help us solve crimes. But in order to take advantage of these tools, a crime scene officer needs to stay up-to-date with the latest developments and understand the capabilities of specialists in the field. Your goal is not to acquire the same level of knowledge as the expert, but to have enough knowledge of the field to recognize what the expert can accomplish with the right evidence. With this knowledge, you can tackle your crime scene in a systematic and thorough manner and provide the experts the evidence they need. In this issue, I’ll give you an overview of some key areas you should focus on when processing a scene.
To begin with, advances in fingerprint technology now allow experts to lift prints from surfaces that couldn’t be processed in the past. Gathering as much fingerprint evidence as possible is always important, so you should still begin by processing surfaces such as vehicles and windows right at the scene. But you should then look for other potential sources of prints. For example, experts can lift latent prints from documents, papers, and adhesive tape. If these items are present, carefully collect them and send them off to be processed by your local or state lab.
DNA, of course, has become a crucial part of crime scene investigation. So much can be done with DNA, but if you don’t have knowledge of what the experts can do, you may miss the opportunity to identify a suspect. Besides looking for hair, blood, and cigarette butt evidence, you should also look for any material the suspect may have come into contact with. Take the time to swab surfaces such as the steering wheel of a vehicle or the grip of a gun. Also remember that if you are fingerprinting and develop smudges with no ridge detail, the smudges can be swabbed for DNA testing. In the past, we couldn’t get DNA from these sources, but now we can. In addition, you should also know that DNA can be retrieved from things like knit caps, baseball caps, and eye glasses. Collect all of these items for the DNA experts and you’ll increase your chances of success.
A good example of a crime scene that requires specialized knowledge is one involving a decomposed body. While a decomposing body presents many challenges, you can gain vital information if you know what evidence to collect and the right expert to contact. You can actually purchase an entomology kit that allows you to process the body right at the scene. By following the directions that come with the kit, you can collect the maggots and other samples from the body. Once you have the necessary samples, you can send them to an entomologist. Through an analysis of the samples, the entomologist can determine how long the body has been at the scene.
Another important type of evidence is blood spatter. A lot of information about homicides or other crimes can be gained by studying the pattern of blood on a surface. Your first step should be to document the evidence with photography and diagrams. Then, depending on the complexity of the evidence, you may also need to bring a blood spatter expert to the scene. Again, your goal is not to acquire the same level of knowledge as the expert, but to have enough knowledge of the field to recognize what the expert can accomplish with the right evidence.
Being knowledgeable about the study of bullet trajectory can prove to be useful for your case. If at least two points of contact exist, experts in this area with the proper equipment, can trace the path of a bullet and thus determine the exact position of the victim and the location of the shooter when the weapon was fired. Once you know the location or area of the shooter, you may discover further evidence such as shell casings. All of this documentation can aid in preparing a strong case for court.
Some of the most important experts you can work with when you are dealing with a homicide are from the medical examiner’s office. Investigators can come to the scene to take their own photographs and notes to supplement yours. Once they have the body at the morgue, they can conduct a variety of tests and examinations that can provide crucial information.
Making use of the expertise of a forensic pathologist can also be essential. While a hospital-based physician may be able to determine the time and cause of death, a forensic pathologist has the training and knowledge to tell you even more about the crime itself. In a case in Topeka, KS, for example, the victim was found floating in a river, shot twice. However, the forensic pathologist was able to determine that the victim was shot twice with a double barreled gun — probably a Derringer — and that the victim had been beaten. The knowledge gained from such an expert can make or break your case. If you don’t have a forensic pathologist available in your town or city, you should get help from your state resources.
Finally, you should also search for shoe and tire track information at the crime scene. If properly documented and collected, this evidence can aid in the prosecution of the case. The crime lab experts can compare the evidence collected at the scene to the suspect’s items.
The common denominator in any crime scene investigation is knowledge: you need to know both your own limits and the capabilities of the experts. Remember, your job is to build the strongest possible case. Once evidence is lost, you can’t go back and recreate it. And if you haven’t collected enough evidence or called in the right experts, you could end up with a case that won’t hold up in court. Don’t stay in the Dark Ages. Take advantage of conferences sponsored by the International Association of Identification (IAI) and courses offered at many colleges and universities. These conferences and courses are an invaluable way to gain the knowledge you need to do your job well.
Dick Warrington is in research and development and a crime scene consultant and training instructor for the Lynn Peavey Company. For the past several years, Dick has been teaching classes throughout the U.S. and Canada, trying to dispel some of those “you can’t do that” myths. Dick can be reached at dwarrington@peaveycorp.com
Reprinted with Permission of Forensic Magazine®. www.forensicmag.com
March 2012