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What Is Forensic Evidence?

Introduction

Forensic evidence is item collected or information gathered through scientific for the use in legal proceedings. During investigation, forensic evidence gathered at the crime scene or during autopsy will be analysed in the laboratory and the result will be presented at the court. Every scene of crime is unique and each case has its own challenges. Death cases or complex crimes require collection, examination and analysis of a large number of evidence.

The importance

The collection of forensic evidence is important in crime investigation and prosecution at the court. Among the importance of forensic evidence are as follows;

  • To prove a crime has been committed or establish key elements of a crime
  • To provide investigative leads for a case
  • To place the suspect in contact with the victim or with the crime scene.
  • To exonerate the innocent
  • To corroborate or to refute suspect’s statement or alibi
  • To induce confession of a suspect
  • To corroborate a witness or victim’s testimony
  • To assist in establishing the facts of what occurred
  • To help in preparing expert’s testimony at the court.

Types of evidence

There are many types of forensic evidences that can be used to help investigators to solve crimes and death cases. Varieties of classification is used to categorize forensic evidence. Generally, forensic evidences belong to three main evidences which are biological, physical and chemical evidence.

  1. Biological evidence

    Biological evidence are samples found from living creature such as blood, saliva, semen, urine, perspiration, bones, hair, stomach content, internal body organs and other bodily fluids. They also include plants and insect such as fly and ant. This evidence are usually collected at the scene of crime or during autopsy. They will be send to laboratory for DNA analysis, toxicology test, blood alcohol level test, drug test or microbiology and histopathology examination.

    Biological evidence that are usually sent for DNA analysis is blood, saliva, semen, perspiration or bones. For toxicology test, specimen that will be send to the lab are usually blood, urine, stomach contents or internal body organs. These biological evidence are always found in homicide cases, sexual crime, suicide and violent crime.


    Blood splash
    (Source: http://www.thes4p.com/wp-content/uploads/2013/07/Dexter_19.jpg)

  2. Physical evidence

    Physical evidence are non-living material such as firearm, glass, paint and includes impression evidence such as fingerprints, footprints, shoeprints, tire marks, tool marks and bite marks. Impression evidence occurs when there is a contact between two objects.

    Fingerprints is accepted as main evidence for unique identification for the individual and even twins with similar DNA has different fingerprints. Knowledge on fingerprints is used to clarify ones identity accurately.

    Physical evidence normally found at burglary, robbery, road traffic accident, hit and run and homicide cases.

    Example of physical evidence


    Pistol
    (Source: http://www.ncids.com/forensic/firearms/firearms.shtml)
     

    Bullet cases
    (Source: http://www.miramarpd.org/property-evidence-crime-scene/)
     

    Fingerprint
    (Source: http://rocketscorner.com/blog/wp-content/uploads/2009/08/latent-from-glass-frag.jpg)

    Screwdriver mark under magnification of microscope
    (Source: http://www.anilaggrawal.com/ij/vol_001_no_002/paper005.html)
     

    Tools that were found at the scene of crime
    (Source: http://rocketscorner.com/blog/wp-content/uploads/2009/08/tools-found-with-poss-suspect.jpg)
     

    Shoe mark
    (Source: http://www.emich.edu/publicsafety/police/services/investigations/evidence.php)
  3. Chemical evidence

    Chemical evidence consist of drugs, medicine, alcohols, powdered associated with firearms, explosive residue, noxious chemicals, lubricants and accelerants from arson debris. These evidences are found in arson, homicide, suicide, robbery and vandalism case.

    Example of chemical evidence


    Cannabis drug
    (Source: http://www.army.mil/article/39994/CID___Putting_the_puzzle_together/)
     

    Gunshot residue
    (Source: http://www.adfs.alabama.gov/FATM.aspx)
         

    Medicine
    (Source: http://www.novinite.com/view_news.php?id=144653)
     
     

Admission in Court

Acceptance and rejection of an evidence related with the integrity of the evidence. Integrity and identity of the evidence can be protected by maintaining the chain of custody starting from the collection of the evidence to the laboratory until result of analysis is released.

In order to maintain the chain of custody, the process of collection and submission for every evidences from any parties to other parties should be documented in detail. Date, time, type of evidence and persons who deliver and receive the evidence must be recorded accurately.

Besides that, integrity and identity of the evidences can be secured by appropriate handling on specimen beginning from process of collecting, packing, labelling, sealing and storing.

 

Source: http://www.dreamstime.com/stock-photography-chain-custody-image3215022

Sealed spesimen
 
Proper handling on specimen and maintaining chain of custody could avoid the integrity and validity of the evidence being questioned at the court. As a result, analysis or examination report can be accepted as evidence. Any mistakes can cause a case being rejected, offenders found not guilty or innocent person convicted guilty.

References

  1. Saferstein, R. (2007). Criminalistics: An Introduction to Forensic Science. 9th Ed. Upper Saddle River, NJ: Pearson/ Prentice Hall.
  2. William, G.E. (2000) Introduction to Forensic Sciences. 2nd Edition. Boca Raton, Florida: CRC Press
  3. Tom, M.E. (2010). The Role and Impact of Forensic Evidence in the Criminal Justice System Final Report
Last Reviewed : 21 October 2014
Writer / Translator : Asrul Fahmi b. Abd Mutalib
Accreditor : Khoo Lay See