Thursday, December 19, 2019

Physical Evidences in Forensic Science - An Overview


Dr. Bhoopesh Kumar Sharma
Forensic Expert & Associate Professor

Evidence is anything in any state of matter (solid, liquid, or gas), in any form (biological, chemical, or physical) that is encountered at the scene of crime and can provide a link between the crime, crime scene, and the criminal. 

Physical Evidence on crime scene

The word "evidence," as it applies to the investigation, refers to a wide range of sources of facts that could potentially persuade the court before the trier of fact to prove or disprove points at issue.

There are several types of evidences, some of them are:

1. Relevant evidence

2. Direct evidence (Testimonial Evidences)

3. Circumstantial evidence

4. Inculpatory evidence
6. Exculpatory evidence 
7. Corroborative evidence 
8. Witness evidence

9. Hearsay evidence

10. Physical evidence

blooded axe

However, in this section, we will only discuss the physical evidences that are encountered at the scene of the crime and can provide a link between the crime and the criminal.

Significance of Physical Evidences:

1) They are more reliable than testimonial evidence 
2) They can prove that a crime has been committed
3) They can corroborate or refute testimony 
4) They can link a suspect with a victim or with a crime scene 
5) They can establish the identity of persons associated with a crime 
6) They can allow reconstruction of events of a crime
7) They are the basis of any crime investigation
8) They can also prove the innocence of wrongly accused person
9) They can prove the nature and type of crime
10) They can prove, whether the crime scene is genuine or staged, etc.

Sources of Physical Evidences: 

2.THE VICTIM (if any)

There are various classifications of Physical Evidences, I am discussing here two major classification (below). However, physical evidences can be classified in may other ways.

physical evidences types

 Precautions During Collection of Physical Evidences:

1.Any temptation of picking up an article immediately on arrival at the scene is to be avoided.

2.They will be collected only after the initial search and the recording.

3.Evidences should be collected with all precautions to avoid destruction or contamination.

4.Each evidence will be collected in separate container.

5.In violent crimes the evidences are collected prior to removal of the body for autopsy.

6.They should be collected by proper method in proper collecting devices.

7.They should be handled properly and to the least to avoid loss or damage.

8.Chain of custody should be maintained.

9. The packing should be proper and secure.

10. Each article should be separately packed and labeled so that the individuality and identity are maintained.

11. As far as possible all packets belonging to one case should be enclosed in a box or outer covering to form a parcel, unless disparity in size of various articles make this impossible.

12. The exhibits inside the packing, do not come in contact with each other.

13. The exhibits do not spill due to the use of unsuitable lids and stoppers.

14. The container should be strong enough to avoid damage in transit.

15. The labels should be numbered and should bear the signature of the forwarding officer along with the case details.

16. The topside of the box is always indicated on the top of the box and marked “Handle with Care”.

17. The exhibits should be sent through a special messenger as far as possible.

18. The exhibits should be properly sealed.

19. For Minute traces of hairs, fibers, dust, soil, glass and paint vacuum sweepings is done at the scene.

20. It may be necessary to take custody of all clothing worn by  the participants in a crime.  Sweepings from each area of a crime scene must be collected and packaged separately.

   21. Fingernail scrapings are to be taken with a blunt instrument, like a toothpick.  The scrapings are to be collected and packaged separately for later microscopic examination. 

22. If there is a deceased victim, the body will be autopsied by a medical examiner or coroner to collect evidence.
23. They will be working to determine the cause of death, as well as collecting evidence.

24. Dried stains on the immovable items are to be swabbed for further analysis. Cotton swab can be moistened with distilled water or saline

25. Blood, hairs, fibers, soil particles, and other types of trace evidence should not be removed from garments, weapons, or other articles.  The entire object should be sent to the lab for processing.
26. Liquid biological fluids, to be collected with the help of droppers/pipettes and then transferred to appropriate vials.

27.If evidence is found adhering to a large structure, such as a door, wall or floor; remove the specimen with a forceps or appropriate tool.  In the case of a bloodstain, one may either scrape the stain off the surface or transfer the stain to a moistened swab, or cut the area of the object bearing the stain.
28. Wet stains should be air dried first and then packed in a proper ventilated paper bags.

29. Trace evidences should be collected in the plastic zip pouches. Each different item or similar items collected at different locations must be placed in separate containers.

30. Weapons/Tools should be collected in appropriate sized cardboard boxes along with avoidance of any movement.

31. Bullets collected from the scene of crime can be packed separately along wrapped in cotton to avoid any movement that can create further marking.

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