The Importance of Impression Evidence
Impression evidence is the kind of evidence sought after to keep a crime scene investigation progressing forward. Objects retain their characteristics or create an “impression” on another physical object within a crime scene, when they are stamped or pressed against each other. Due to these impressions being hard to notice and/or recognize, they are often easily missed. Therefore, it is extremely important that everything is rechecked carefully, so as not to miss any evidence, namely an impression.
This type evidence is categorized in two ways: Either hard, or soft impressions. Determining the length and width of the object leaving the mark is done in a 2 dimensional aspect. 3 dimensional measuring adds depth to the image of the object as well. The 3 dimensional measuring therefore, of course, leaves a better chance at crime scene investigators to see what kind of object left the impression.
The importance to investigation
Small objects, utensils, and measurement devices are used to go through evidence, as you can see on many TV shows. Stuff caught by monitoring that the naked eye can not typically perceive is what these tools do, and the use of them allow CSI to correctly assess and analyze evidence.
One main example and the most well known form of impression evidence, would be fingerprinting. DNA is used to profile any impression lifted from the site. Courts recognize this as a valid process, and as such, the evidence is always used in court proceedings.
Impression Evidence Types
Many types exist, though a few are more commonly known than others. Each of them put together will allow CSI to discern what happened and who in most cases. If strong enough, the impression evidence can definitely lead to the direct identity of a person.
Fingerprinting
Whenever a person touches something, it will leave this type of evidence. Not typically visible to the naked eye, CSI use a certain powder to make the prints visible and retrievable. This type of evidence is always held by a court as a valid identifier to a person having committed a crime.
Footprints
The process involved in this is about the same as for fingerprinting. The equipment and protocol and procedure are identical. Every floor, tire tracks, counter tops, every surface is looked at. They use a type of tape to lift the impression of after it is retrieved by mechanical means. They can then be used to make a proper ID.
Tool marks
Entrances are where this form of evidence is typically found. They use this type to discern what kind of tools or what methods were used to gain entry to any particular house, apartment, or building.
Tire Tread
Tire impressions left on dirt and in soil are used to find out about a suspect when they have escaped in a vehicle. Though, some surfaces, namely that of thick carpets or even grass tend to have their readability lessened because they spring back after having been ridden through. They can still be vital to solving a scene though, by pointing the investigation in the direction of a suspect and where they drive off to.
