How Crime Scene Investigation Works

May 29, 2016 | Author: Maja | Category: Types, Research, Science
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If you ever want to be CSI, this is your manual......


How Crime Scene Investigation Works

On TV shows like "CSI," viewers get to watch as investigators find and collect evidence at the scene of a crime, making blood appear as if by magic and swabbing every mouth in the vicinity . Many of us believe we have a pretty good grip on the process, and rumor has it criminals are getting a jump on the good guys using tips they pick up from these shows about forensics. But does Hollywood get it right? Do crime scene investigators Photo courtesy FBI follow their DNA samples into the lab? Do they interview suspects and catch the bad guys, or is their job all about collecting physical evidence? In this article, we'll examine what really goes on when a CSI "processes a crime scene" and get a real-world view of crime scene investigation from a primary scene responder with the Colorado Bureau of Investigation.

Thanks! Special thanks to Joe Clayton, Laboratory Agent and primary scene responder for the Colorado Bureau of Investigation, for his generous assistance with this article.

Who's at the Scene? Police officers are typically the Crime scene investigation is the meeting point of science, logic and first to arrive at a crime scene. law. "Processing a crime scene" is a long, tedious process that They arrest the perpetrator is involves purposeful documentation of the conditions at the scene he's still there and call for an and the collection of any physical evidence that coul d possibly ambulance if necessary. They illuminate what happened and point to who did it. There is no are responsible for securing the typical crime scene, there is no typical body of evidence and there scene so no evidence is is no typical investigative approach. destroyed. The CSI unit documents the At any given crime scene, a CSI might collect dried blood from a crime scene in detail and collects windowpane -- without letting his arm brush the glass in case there any physical evidence. are any latent fingerprints there, lift hair off a victim's jacket using The district attorney is often tweezers so he doesn't disturb the fabric enough to shake off any present to help determine if the of the white powder (which may or may not be cocaine) in the folds investigators require any search of the sleeve, and use a sledge hammer to break through a wall warrants to proceed and obtain that seems to be the point of origin for a terrible smell. those warrants from a judge. All the while, the physical evidence itself is only part of the The medical examiner (if a equation. The ultimate goal is the conviction of the perpetrator of homicide) may or may not be the crime. So while the CSI scrapes off the dried blood without present to determine a smearing any prints, lifts several hairs without disturbing any trace preliminary cause of death. evidence and smashes through a wall in the living room, he's Specialists (entomologists, considering all of the necessary steps to preserve the evidence in forensic scientists, forensic its current form, what the lab can do with this evidence in order to psychologists) may be called in if reconstruct the crime or identify the criminal, and the legal issues the evidence requires expert involved in making sure this evidence is admissible in court. analysis. Detectives interview witnesses and consult with the CSI unit. They investigate the crime by following leads provided by witnesses and physical evidence.

The investigation of a crime scene begins when the CSI unit receives a call from the police officers or detectives on the scene. The overall system works something like this: • The CSI arrives on the scene and makes sure it is secure. She does an initial walk-through to get an overall feel for the crime scene, finds out if anyone moved anything before she arrived, and generates initial theories based on visual examination. She makes note of potential evidence. At this point, she touches nothing. • The CSI thoroughly documents the scene by taking photographs and drawing sketches during a second walk-through. Sometimes, the documentation stage includes a video walk-through, as well. She documents the scene as a whole and documents anything she has identified as evidence. She still touches nothing. • Now it's time to touch stuff -- very, very carefully. The CSI systematically makes her way through the scene collecting all potential evidence, tagging it, logging it and packaging it so it remains intact on its way to the lab. Depending on the task breakdown of the CSI unit she works for and her areas of expertise, she may or may not analyze the evidence in the lab. • The crime lab processes all of the evidence the CSI collected at the crime scene. When the lab results are in, they go to the lead detective on the case. Every CSI unit handles the division between field work and lab work differently. What goes on at the crime scene is called crime scene investigation (or crime scene analysis), and what goes on in the laboratory is called forensic science. Not all CSIs are forensic scientists. Some CSIs only work in the field -- they collect the evidence and then pass it to the forensics lab. In this case, the CSI must still possess a good understanding of forensic science in order to recognize the specific value of various types of evidence in the field. But in many cases, these jobs overlap. Joe Clayton is a primary crime scene responder at the Colorado Bureau of Investigation (CBI). He has 14 years of field experience and also is an expert in certain areas of forensic science. As Clayton explains, his role in laboratory analysi s varies according to the type of evidence he brings back from the crime scene: Depending on what scientific examinations are needed or requested, I may be involved in the actual "bench work" once the evidence is submitted to the laboratory. I have expertise in blood pattern identification (blood spatter), trajectory determination, serology (blood and body fluids), and photography. I also have knowledge in many other areas (firearms, fingerprints, questioned documents...) that may assist me at the scene. As a primary crime scene responder at the CBI, my role at the scene may involve one or more of my particular disciplines. While I would not do a functionality test on a firearm here at the laboratory, my role at the crime scene would be to collect the gun and understand its potential evidentiary significance. Crime scene investigation is a massive undertaking. Let's start at the beginning: scene recognition.



Photo courtesy Naval Medical Center Portsmouth, VA




Joe Clayton's photography kit: He usually uses a digital Nikon D100 to photograph a crime scene. He might also use a Nikon N8008s (35-mm film format) for special applications. Overview shots are the widest possible views of the entire scene. If the scene is indoors, this includes: • views of all rooms (not just the room where the crime seems to have occurred), with photos taken from each corner and, if a boom is present, overhead • views of the outside of the building where the crime happened, including photos of all entrances and exits • views of the building showing its relation to surrounding structures • photos of any spectators at the scene These last shots might identity a possible witness or even a suspect. Sometimes, criminals do actually return to the scene of the crime (this is particularly true in arson cases). Mid-range photos come next. These shots show key pieces of evidence in context, so the photo includes not only the evidence but also its location in a room and its distance from other pieces of evidence. Finally, the CSI takes close-ups of individual pieces of evidence, showing any serial numbers or other identifying characteristics. For these pictures, the CSI uses a tripod and professional lighting techniques to achieve the best possible detail and clarity -- these photos in particular will provide the forensics lab with views to assist in analyzing the evidence. The CSI also takes a second set of closeup shots that includes a ruler for scale. Every photo the CSI takes makes it into the photo log. This log documents the details of every photo, including the photograph number, a description of the object or scene in the photograph, the location of the object or scene, the time and date the photograph was taken and any other descriptive details that might be relevant. Without a good photo log, the pictures of the scene lose a lot of their value. In the investigation of John F. Kennedy's assassination, the FBI photographers who attended the autopsy didn't create descriptions of the pictures they were taking, and investigators were later unable to distinguish between entrance and exit wounds in the photos. Sketches In addition to creating a photographic record of the scene, CSIs also create sketches to depict both the entire scene, which is easier to do in a sketch than in a photograph because a sketch can span several rooms, and particular aspects of the scene that will benefit from exact measurements. The goal is to show locations of evidence and how each piece of evidence relates to rest of scene. The


Cleanup Crews Crime scene investigators do not clean up the scene -- neither do police officers, detectives or anyone else involved in the investigation. The task of cleaning up a gruesome crime scene often falls to the victim's family members. In the last 10 years, however, some people have recognized the need for hired crimescene cleaners to take care of the job so family members and landlords don't have to, and some of these people have formed companies dedicated to the task. It's a dirty, sometimes hazardous, very high-paying job. Crime-scene clean-up can run up to $200 an hour on top of flat fees (in the thousands) and equipment costs. Cleaning up a meth lab is especially expensive because of the risk to anyone who enters the scene and the amount of work involved in making the area habitable again.

At the Crime Scene: Finding the Evidence The goal of the evidence-collection stage is to fin d, collect and preserve all physical evidence that might serve to recreate the crime and identify the perpetrator in a manner that will stand up in court. Evidence can come in any form. Some typical kinds of evidence a CSI might find at a crime scene include: • Trace evidence (gunshot residue, paint residue, broken glass, unknown chemicals, drugs) Photo courtesy U.S. Aid • Impressions (fingerprints, footwear, tool marks) • Body fluids (blood, semen, saliva, vomit) • Hair and fibers • Weapons and firearms evidence (knives, guns, bullet holes, cartridge casings) • Questioned documents (diaries, suicide note, phone books; also includes electronic documents like answering machines and caller ID units)

With theories of the crime in mind, CSIs begin the systematic search for incriminating evidence, taking meticulous notes along the way. If there is a dead body at the scene, the search probably starts there. Examining the body A CSI might collect evidence from the body at the crime scene or he might wait until the body arrives at the morgue. In either case, the CSI does at least a visual examination of the body and surrounding area at the scene, taking pictures and detailed notes. Before moving the body, the CSI makes note of details including: • Are there any stains or marks on the clothing? • Is the clothing bunched up in particular direction? If so, this could indicate dragging. • Are there any bruises, cuts or marks on body? Any defense wounds? Any injuries indicating, consistent with or inconsistent with the preliminary cause of death? • Is there anything obviously missing? Is there a tan mark where a watch or ring should be? • If blood is present in large amounts, does the direction of flow follow the laws of gravity? If not, the body may have been moved. • If no blood is present in the area surrounding the body, is this consistent with the preliminary cause of death? If not, the body may have been moved. • Are there any bodily fluids present beside blood? • Is there any insect activity on the body? If so, the CSI may call in a forensic entomologist to analyze the activity for clues as to how long the person has been dead. After moving the body, he performs the same examination of the other side of the victim. At this point, he may also take the body temperature and the ambient room temperature to assist in determining anestimated time of death (although most forensic scientists say that time of death determinations are extremely unreliable -- the human body is unpredictable and there are too many variables involved). He will also take fingerprints of the deceased either at the scene or at the ME's office. Once the CSI is done documenting the conditions of body and the immediately surrounding area, technicians wrap the body in a white cloth and put paper bags over the hands and feet for transportation to the morgue for an autopsy. These precautions are for the purpose of preserving any trace evidence on the victim. A CSI will usually attend the autopsy and take additional pictures or video footage and collect additional evidence, especially tissue samples from major organs, for analysis at the crime lab. Examining the scene There are several search patterns available for a CSI to choose from to assure complete coverage and the most efficient use of resources. These patterns may include: • The inward spiral search: The CSI starts at the perimeter of the scene and works toward the center. Spiral patterns are a good method to use when there is only one CSI at the scene.





While searching the scene, a CSI is looking for details including: • Are the doors and windows locked or unlocked? Open or shut? Are there signs of forced entry, such as tool marks or broken locks? • Is the house in good order? If not, does it look like there was a struggle or was the victim just messy? • Is there mail lying around? Has it been opened? • Is the kitchen in good order? Is there any partially eaten food? Is the table set? If so, for how many people? • Are there signs of a party, such as empty glasses or bottles or full ashtrays? • If there are full ashtrays, what brands of cigarettes are present? Are there any lipstick or teeth marks on the butts? • Is there anything that seems out of place? A glass with lipstick marks in a man's apartment, or the toilet seat up in a woman's apartment? Is there a couch blocking a doorway? • Is there trash in the trash cans? Is there anything out of the ordinary in the trash? Is the trash in the right chronological order according to dates on mail and other papers? If not, someone might have been looking for something in the victim's trash. • Do the clocks show the right time? • Are the bathroom towels wet? Are the bathroom towels missing? Are there any signs of a cleanup? • If the crime is a shooting, how many shots were fired? The CSI will try to locate the gun, each bullet, each shell casing and each bullet hole. • If the crime is a stabbing, is a knife obviously missing from victim's kitchen? If so, the crime may not have been premeditated. • Are there any shoe prints on tile, wood or linoleum floors or in the area immediately outside the building? • Are there any tire marks in the driveway or in the area around the building? • Is there any blood splatter on floors, walls or ceilings? The actual collection of physical evidence is a slow process. Each time the CSI collects an item, he must immediately preserve it, tag it and log it for the crime scene record. Different types of evidence may be collected either at the scene or in lab depending on conditions and resources. Mr. Clayton, for instance, never develops latent fingerprints at the scene. He always sends fingerprints to the lab for development in a controlled environment. In the next section, we'll talk about collection methods for specific types of evidence.

Consider This • Crime scenes are three dimensional. CSIs should remember to look up. • If a CSI shines a flashlight on the ground at various angles, even when there's plenty of lighting, he'll create new shadows that could reveal evidence. • It's easy to recover DNA from cigarette butts.

Evidence Collection





Powders and brushes at the CBI latent-fingerprint lab • Chemicals (for porous surfaces): Iodine, ninhydrin, silver nitrate The CSI sprays the chemical onto the surface of the material or dips the material into a chemical solution to reveal the latent print. • Cyanoacrylate (Super Glue) fuming (for porous or non-porous surfaces) The CSI pours Super Glue into a metal plate and heats it to about 120 F. He then places the plate, the heat source and the object containing the latent print in an airtight container. The fumes from the Super Glue make the latent print visible without disturbing the material it's on. Footwear Impressions and Tool Marks A latent fingerprint is an example of a two-dimensional impression. A footwear impression in mud or a tool mark on a window frame is an example of a three-dimensional impression. If it's not possible to submit the entire object containing the impression to the crime lab, a CSI makes a casting at the scene.




Analyzing the Evidence: Forensic Science The first forensics lab in the United States opene d in 1923 in Los Angeles. In 1932, the FBI established its own forensics lab to serve police departments and other investigating authorities all over the country. The FBI lab is one of the largest in the world. The Denver Crime Lab at the Colorado Bureau of Investigation provides evidence collection and laboratory analysis for any police department in Colorado that requests its services. It also conducts state investigations that don't fall under the jurisdiction of any local authority. Some specialty departments in the Denver Crime Lab include: • Latent fingerprints and impressions Develop latent fingerprints; analyze and compare fingerprints, footwear and tire impressions; run fingerprints through the Automated Fingerprint Identification System (AFIS, which utilizes the FBI database) for comparison against hundreds of millions of prints

CBI technicians use these camera setups to photograph recovered prints to use in comparison and for running through the AFIS system. On the left is an old-school Polaroid setup, and on the right is a digital-camera setup. Mr. Clayton prefers the Polaroid results. • Trace evidence Run GSR analysis; identify and compare samples of soil, glass, fibers and paint • Chemistry Conduct analysis and comparison of illicit drugs, explosives and unknown chemicals • Computer Crimes Recover evidence from computers; perform computer enhancement on audio or video evidence • Firearms and toolmark identification Identify firearms; test firearms to establish barrel pattern and distance of gun from entrance wound; identify and compare bullets, casings and toolmark impressions • Serology and DNA Conduct body fluid analysis, including DNA analysis for blood stains, semen and hair for identification and comparison

Comparison microscope setup in the CBI serology lab • Questioned documents Detect forgery and alterations; conduct handwriting comparisons; reconstruct destroyed documents; identify and compares printers, typewriters or copiers used to produce a document Often, a piece of evidence passes through more than one department for analysis. Each department delivers a complete report of the evidence it analyzed for the case, including the actual results (numbers, measurements, chemical contents) and any expert conclusions the scientists have drawn from these results. The CSI in charge might compile the results and deliver them to the lead detective on the case, or the lab might send the results directly to the detective squad.


CSI vs. "CSI"

So, does Hollywood get it right? When asked if the TV show "CSI" accurately depicts his job , Joe Clayton's short answer was, "No." The long answer was that the show does accurately represent certain aspects of crime scene investigation, but it leaves a lot out Photo courtesy HSW Shopper and it adds a lot because, well, it's Hollywood. Viewers don't want to watch a bunch of CSIs waiting around for a search warrant, and they would probably be unsatisfied if they never got a look at the suspect. Scientifically speaking, "CSI" sometimes misses the mark. In reality, it's not possible to come up with a two-hour range for the time of death. Also, you don't just scan a fingerprint into a computer and wait for it to spit out a photo of the suspect. Fingerprint-comparison software returns several possible matches that an expert then analyzes visually to determine a definite match. Other places where Hollywood gets it wrong involves investigative process. Crime scene investigators almost always get warrants before searching a scene. Pretty much the only scene that might not


Becoming a CSI CSIs work long hours, must be available for emergencies 24/7 and often deal with gruesome scenes. For Joe Clayton, his job as a CSI involves constant reminders of man's inhumanity to man. But he views his job as a chance to use science to help people. CSIs can be police officers or civilians. The most common way to become a CSI is to become a police officer first and then receive CSI training. All police departments and law-enforcement agencies have different criteria. Typically, a civilian CSI should have a twoor four-year degree. Mr. Clayton is not a police officer. He graduated from college with a bachelor's degree in biology and minors in chemistry and behavioral sciences. He applied for a CSI position at the Kansas Bureau of Investigation and received his training there. Call your local police department or crime lab to find out what their requirements are for civilian CSIs. Before deciding to pursue the job, you should visit a morgue and have a look at a mangled body -- if you pass out, consider another career.

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