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What is the general procedure of examining a crime scene?

Documenting A Crime Scene

Richard Saferstein (Former Chief Forensic Scientist) gives expert video advice on: What is the general procedure of examining a crime scene?; How do police isolate and secure a crime scene?; How does an investigator perform a search at a crime scene? and more...

What is the general procedure of examining a crime scene?

At the crime scene we first must isolate it and secure it. We must make sure we don't have people walking around that crime scene, trampling all over it, and inadvertently destroying the evidence. Once that is accomplished, we then can go about to systematically search the scene, search it in a way that we cover the entire scene in a systematic way so that every item of relevance is identified, collected, and preserved. And at the same time, we must document the scene. We must photograph it, we must sketch it, we must have thorough note-taking. Because all of this documentation will come into play when we go to court and the state or the prosecution presents its case to the judge and to the jury. But the important thing to remember is that forensic science begins at the crime scene, and it's all going to be lost if that area of the crime cannot be properly preserved.

How do police isolate and secure a crime scene?

One of the easiest things to do is to put up a tape around the scene to define the perimeter of the crime scene. Of course you also want to station police personnel at key areas of the scene to keep individuals out of the scene. If anyone has to enter the scene there should be a log that is kept so each of these individuals are identified and accounted for. There will usually be an individual who we'll designate as the lead investigator. That person is responsible for generally overseeing the crime scene.

How does an investigator perform a search at a crime scene?

What's important is that the search for physical evidence must be systematic. Normally a lead investigator will be assigned to oversee that systematic search, and that lead investigator may conduct the search himself or herself, or may assign others to conduct the search, but it has to be systematic. It may require walking up and back in a straight line . It may require walking in a circular fashion around the crime scene, or it may require sectioning off the crime scene, and having different investigators search in different areas of the scene. A lot will depend on the complexity of the scene, on the area of the scene, the geographical area of the scene, so every scene is very individualist, but the investigators ultimately bring their experience and knowledge to the fore to carry out that mission.

What type of physical evidence does an investigator look for at a crime scene?

There are certain items that we see on a repeated basis at crime scenes, such as hairs, fibers, paint chips, glass, guns, bullets, cartridges, and different types of ropes. Also, what's interesting and very important are these carriers of physical evidence - things that we see at scenes that somebody may have touched with their lips or their fingers and have deposited a finger print or DNA onto. We're not going to know much about that until we get it back to the crime lab and we have it analyzed.

How does an investigator document physical evidence at a crime scene?

The recording of physical evidence at the crime scene is normally accomplished in three ways. The first is the note taking. The investigator will thoroughly document what he or she sees in his or her observations. This can be handwritten notes, but it also could be accomplished through a tape recorder. The second way of documenting the crime scene is through photographs. The crime scene must be thoroughly photographed. All items of evidence seen at the crime scene must be photographed, and it must be photographed in a way that shows us an overview of the item of evidence, such as a cigarette butt where it's present in relationship to the entire crime scene. There perhaps would then be a mid-range view of that item of physical evidence, the cigarette butt, in this case. Ultimately, before it's collected, a nice close-up shot of the physical evidence should be taken. Once that's accomplished, the crime scene investigator will roughly sketch the scene showing where items were found, where they were collected. Ultimately, that sketch will be brought back to the police station where an artist may finish it up and make for a nice presentable finished sketch, or the sketch may be documented through a CAD (computer aided digital system), ultimately for presentation in the courtroom.

How is crime-scene reconstruction used in CSI?

It really is an effort at developing a timeline, from the time the crime was initiated until the perpetrator left the crime scene, and what took place during that interval. Many skills are brought to observe in reconstructing a crime scene. You have the pathologist or the medical examiner. You have the police investigators who have questioned eye witnesses. You have the forensic scientists who've looked at items of physical evidence that have been collected at the scene. All of these skills are brought to bear to make an effort at determining a timeline, what occurred at the very beginnings of the scene and what occurred at the termination of the crime scene, or of the crime. That is what crime scene reconstruction is all about.