June 13, 2020

Forensic Analysis: Implications of proper evidence collection, storage

 By Queen Edet Nkpubre

A crime scene that has been correctly identified and cordoned off can contain a lot of evidence that needs to be collected and stored properly for it to be in good condition for analysis at any time. Evidence properly preserved can even be used for cases many years later.

Almost any item can serve as evidence – from biological material such as semen, blood, and saliva, to physical/trace evidence such as footprint, soil, and more. Each evidence type has its special collection and storage method which needs to be taken into consideration by crime scene police officers.

Wet and dry evidence are stored differently. Although direct evidence is good to have such as a confession, there are cases where there are no witnesses, or none are willing to come forth and so such a case would rely heavily on circumstantial evidence found at a crime scene.

READ ALSO: Forensic handwriting analysis

The evidence, therefore, becomes the silent witness. There is some evidence that carries strong implications if found at a scene. One such is DNA (deoxyribonucleic acid) which is the carrier of genetic/hereditary information and present in all human beings.

It is unique to an individual except for identical twins which have matching profiles, however, there are recent studies that suggest a new way to tell apart the DNA of identical twins.

Proper collection of evidence at a crime scene begins with protection – each crime scene officer must be fully kitted before entering a crime scene. Also, there should be a registration sheet where all crime scene officers record their names, time of entry, and time of exit at the scene. Officers should avoid sneezing and coughing during collection.

Various items at a scene could serve as evidence and should not be discarded or overlooked. An example of evidence is any item with DNA-containing samples on them. DNA sources include blood, saliva, semen, hair, and even fingerprint. During my Master’s program in Forensic Science at the University of Strathclyde, my research topic on Touch DNA led me to findings others had made that fingerprints, although primarily collected for their pattern analysis, often contain DNA material which can be analyzed.

Biological samples such as these can be found on anything at the crime scene from furniture, weapons, clothing, underwear, and on the body of a victim if present.

Any item these is found on should be collected with gloved hands, lest the officer implicates himself in the crime he’s investigating! The Officer McKie case in 1997 is one of the biggest cases where a police officer’s fingerprints were said to have been found at a murder scene.

Once the evidence has been located and had evidence markers placed close to them, the proper collection is the focus because evidence not collected properly can be contaminated or damaged and therefore compromised.

Hair samples must be picked using tweezers, and then stored in an envelope which is then placed in a bigger paper bag. Where evidence can be stored in bags, paper bags should be used rather than plastic/nylon bags. Glass shards can be stored in paper boxes.

READ ALSO: Criminal profiling: The forensics that links a crime scene behavior to a suspect

Biological samples such as semen found on underwear or bedsheets or blood on clothing should be allowed to dry before storage in a paper bag. A pool of blood at a scene can be collected using a sterile cotton cloth.
It should be left to dry and stored in a fridge. All collected items must be sealed and labeled. This should also be stored securely with an adequate chain of custody maintained to track each handler of the evidence and deter manipulation of evidence.

The practice of proper collection and storage on evidence plays a huge role in justice being served as it prevents contamination, manipulation, and damage of evidence which can lead to a miscarriage of justice.

This practice can be the difference between the wrong person being convicted, and the actual perpetrator of the crime walking free in society and able to commit more crimes.

It can be a saving grace even many years later, as well-preserved evidence is often the foundation of cold cases being solved when a new technology emerges, or new laws are passed in a state or country,