They say that you don't really understand a topic until you teach it. I am never really sure who "they" are, but I can certainly attest after only two years as a university level instructor, that "they" are correct.

After 16 years of experience in law enforcement working countless crime scenes, I started teaching college students and cops the basics of crime scene investigation. I read every text I could find, performed countless "Google" searches and read every periodical I could get my hands on. I was finally ready to teach "crime scene search patterns." I taught lane searches, zone searches and the famous CWA search (the "Cop Wondering Around" search; not recommended, by the way).

My class full of officers seemed to understand the basics, so off we went to the crime scene "house" to practice what we learned. I watched officer after officer find a piece of evidence on the ground and then accidentally kick it, step on it or destroy it in some way while searching for other evidence. Officers would place tent markers on items of evidence to clearly mark them and then place junk out of a drawer on top of the items before they could be collected. Someone even lifted a mattress to look underneath and the mattress slid of the other side of the bed, crushing a piece of evidence! I realized then that all the methods I'd been teaching had failed and decided to come up with a way to search crime scenes that would keep evidence in tact. The solution: searching in stages. This seems to be easily understood by learners and more importantly, works solidly in the real world of CSI.

Level One Search: This is the most basic and superficial search. First, a search pattern is chosen that would be most effective for the crime scene environment to be examined. For example, a "zone" search would be chosen for a small apartment, while a "grid" search might be chosen for a large open outdoor area.

I always recommend switching officer positions and completing a search pattern a second time so that another set of eyes reviews every search. Additionally, the crime scene commander should not become a searcher, but should remain free to make evaluative decisions about what constitutes evidence and to coordinate the numbering of all found potential evidence.

As evidence is located, the commander makes a decision as to whether the item is potential evidence and if so makes a second decision concerning what number that particular piece should be. After this process, an evidence marking device is placed near the evidence. When conducting a level one search, the officer's eyes are the only tools used. Nothing is touched; therefore this is the least invasive form of search. The only items of evidence searched for are those that can be detected without moving any object in the scene.

Once all officers have completed the search and the pattern is double checked, all items are prepared for collection before the level two search. At a minimum this includes, a midrange photo (hopefully over-all photos were taken before the scene was searched or altered in any way), a close up photo (with ABFO scale) and measurement to the item from two fixed points for a sketch. Video taping may or may not fit in here depending on your department policy. Once all evidence items are collected and properly packaged, you can proceed to a second level search. What about the marking device? Leave it in place in case there is any question later about the interrelationship of the location of evidence items collected.

Level Two Search: Even when taking the search process to a more thorough level, crime scene integrity can still be maintained. A level two search consists of moving items that cause minimal intrusion into the scene. For example, when conducting a level two search closet doors are opened, furniture is searched underneath and some drawers may be opened. The idea of a level two search is to not be extremely intrusive, but to search in reasonable places in a way that does not totally disrupt your crime scene. As with a level one search, a search pattern is chosen and double checked. Items are marked with a number and then "caught up" with all the other items previously collected.

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