By: Don Penven
An Introduction to Impression Evidence
It’s been more years than I can remember when I first heard the term “Moulage.” It was an old detective movie and one of the officers at a crime scene suggested making a moulage of footprints near a body. We certainly don’t hear this term used much anymore.
Moulage in French means “casting,” and today the term is used by some to describe a form of makeup used to simulate wounds on the body for EMT training purposes.
Casting is the accepted term used at crime scenes and it refers to making casts of 3-dimensional evidence like toolmarks, footprints and tire tracks. But I’m getting ahead of this story…
In his book, “Footwear…The Missed Evidence,” Dwayne S. Hilderbrand, M.Ed., states: In almost every criminal investigation it is necessary to determine and prove that a particular person or persons may or may not have been present at the scene of a crime. For this reason, the collection, preservation and analysis of physical evidence has become more frequent in the law enforcement community.
Around 1910, a criminologist by the name of Edmond Locard arrived at a theory that every time something comes into contact with another it either takes or leaves a portion of itself or another. This theory is called the Edmond Locard Theory, which simply states "Every contact leaves its trace." This theory is continually used today in crime scene investigations and the analysis of physical evidence.
Since criminals must enter and exit crime scene areas it should therefore, be reasonably assumed that they may leave traces of their footwear. Criminals have become smarter and wiser by beginning to frequently wear protection over their hands to avoid leaving fingerprints, and masks over their faces to avoid eyewitness identification. However, they are rarely aware of, or make little attempt to conceal footwear. During an every- day routine it is normal to see an individual wearing gloves, but it's not normal to see individuals wearing protection over their shoes.
The CasTips-series of articles on this blog is an attempt to bring more crime scene investigators under the awareness that impression evidence can serve as silent testimony in criminal cases, but the biggest problem is that all too often it is overlooked or accidentally damaged or destroyed.
Impression evidence can become apparent in two forms:
- 2-Dimensional: This type of evidence includes dust or dirt prints, blood prints (footwear and fingerprints) or shoe prints in some foreign substance such as oil or grease on a garage floor.
- 3-Dimensional: This type is usually the most visible form of 3-D impressions that are left behind in soft or wet soil, sand and snow. Touching wet paint or soft foods like butter or cheese are forms of evidence left behind by the perpetrator.
The effectiveness of crime scene security often determines if impression evidence will be available. The most fragile form, the type most often overlooked or destroyed, is dust print evidence. This is due largely to the intrusion of the first responders including emergency medical as well as law enforcement personnel. What is often lacking is formal training and an awareness of the fact that dust impression are often found in the tidiest of structures, let alone some of the hovels you may encounter.
The initial officer on the scene is the key to impression evidence survival, and these individuals must be given the awareness of just how valuable impression evidence can be. Protecting the crime scene is vital, but all too often it becomes impractical when serious injuries of victims are apparent. Still, keep in mind that the perpetrator will most often follow a distinctive, direct course through a structure so it behooves the initial responders to avoid stepping in areas along the probable course taken by the perp. Simply put, walk along the walls and avoid open areas of flooring—especially non-carpeted flooring.
A series of articles will follow this post covering the most popular—yet the most effective means of recording and recovering impression evidence.
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