Robert E. Kramer
The dawn of a new age has arrived in law enforcement in the form of DNA research and testing. We in law enforcement, especially those of us working the crime scenes need to be
aware of what we can do "in the field" to assure that proper evidence collection techniques are followed. Only then will the groundwork for successful evidence examinations be in place when we submit the case to a forensic laboratory for analysis.
Polymerase Chain Reaction
Polymerase Chain Reaction (PCR) is the DNA evidence analysis technique which is being practiced at the state laboratory at the Division of Criminal Investigation in Des Moines. PCR is a sensitive, fast, and highly discriminatory method of analysis. One of the most essential aspects of DNA evidence analysis at the lab is that a basis knowledge of evidence collection principles is necessary at the initial stage. PCR allows the criminalist to examine evidence which has been properly collected and preserved with expectations that accurate results will be found as result of the analysis.
Impact and Exchange
It is widely embraced within the law enforcement forensic field that, to at least some degree, the process of impact and exchange occurs at every crime scene. For example, a "run" vehicle impacts the accident scene and exchange occurs with the transfer of paint to the victim vehicle; a burglar impacts a scene with the approach of the area, and exchange occurs when footwear impressions are left behind. As law enforcement officers and crime scene specialists, it is our job to collect and preserve evidence at the scene - evidence which may not only connect the suspect to the scene - but connect the suspect to the incident itself.