This is the third article in our series Ask a Cop. Send your questions for the Bainbridge Island Police to contact@insidebainbridge.com. We’ll get your answers and post them here.
BIPD Detective Aimee LaClaire provided the answers.
Dear BIPD:
Maybe I watch too much TV, but aren’t you supposed to leave a crime scene alone until the cops come? It seems like in the Police Blotter I’m often reading about people who call the police days after finding they’ve been burgled or right after they’ve tidied up their prowled car.
Thank you very much for your question regarding this important and sometimes overlooked aspect of law enforcement. You are correct: It is best to leave a crime scene alone until the police arrive. This gives law enforcement the opportunity to determine if there is anything of evidentiary value that could assist in the identification, apprehension, and prosecution of the suspect(s).
How hard does that make your job?
Someone cleaning up and disturbing a crime scene does not necessarily make our job harder but it does make it more difficult to locate and identify potential evidence. It can also make it difficult to attempt to recreate what happened if the scene is disturbed. Crime Scene Reconstruction is a tool that can be used on major cases to assist in determining what happened and who may have committed the crime.
Also what kind of evidence does the BIPD try to collect at a crime scene?
Crime scenes, however large or small, important or seemingly innocuous, provide clues and details. They follow Locard’s Exchange Principle, which holds that the suspect will bring something into the crime scene and take something away from the crime scene. Dr. Edmond Locard was a French pioneer in the field of forensic science who formulated the basic premise that “Every contact leaves a trace.”
So, if you enter, touch, alter, or clean up a crime scene prior to police processing it for evidence, not only may you destroy or erase potential incriminating and/or exculpatory items, but you may deposit your own hair, fibers, fingerprints, and DNA into the scene. This can cause cross-contamination where what you deposit mixes with what the suspect deposits. This can invalidate some pieces of evidence and make it difficult to use in a court of law.
BIPD will attempt to collect as much evidence as feasible from a crime scene. This typically involves fingerprints and any biological fluid left behind such as blood. It can also include the careful collection of any tangible object that a suspect left behind on scene. If a crime scene is more involved or extensive, if it is thought to be one is a pattern or spree, or if it relates to a major crime such as a homicide, the processing of the scene can be much more in depth.
What kind of evidence processing can you do at your station?
Officers do not process, analyze, or compare evidence while they are on scene. It is simply a time to try to identify what is evidence, collect it properly, and then submit it to the property room with proper chain of custody. This process documents who handles which items of evidence and in which secure area they are housed. All evidence is handled with latex gloves to avoid cross-contamination and possible destruction of evidence.
Some evidence can be processed at our station while other evidence is sent to the state crime lab. The state crime lab handles requests for identification and/or comparison of DNA evidence, fingerprints, and biological samples. Due to the volume of crimes and the related evidence, the lab has to prioritize and set limits. For example, if a suspect touches something, they leave traces of their DNA on that object. For most misdemeanor and property crimes, the state lab will not routinely process DNA evidence without a special request due to extenuating circumstances. There are also times when BIPD requests assistance from other departments or the WSP crime scene technicians to help process a major scene.
In general, is it always best not to enter, touch, or otherwise disturb a potential crime scene. There are many items of evidence that can be collected and processed from the scene of a crime and may be the only way to help identify and prosecute a suspect.
Thanks again for your question.
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