Physical evidence can be described as any material which can be detected, seen and touched at the scene of crime, which is related to the case and can be proven by scientific investigation. It can be in small or macro in size (UNODC, 2009).
Example of the evidence:
- Based on tools and equipment:
- Shoes, footwear and tyres.
- Hammer; screw-driver and wrench.
- Pipe, faucets and the hose.
- Pistol, bullet, shot bullet and cartridge.
- Parangs, hoe, and iron rods.
- Bomb and bomb shrapnel’s.
- Vehicle and machine.
- Bed, bed-spread, pillow, pillowcase and maybe bed.
- Dresses, cloths and fibre.
- Watch, cellular phone, pen and toothpick.
- Syringe and nail clipper.
- Cup, pots, knife and kitchen ware.
- Check book, receipt, suicide note and tissue.
- Based on biological substances:
- Blood, saliva, vaginal secretion, seminal stains and mucous.
- Hair and fibre.
- Internal organ and skin.
- Pollen, seeds and leaves.
- Insects and animals.
- Based on chemical substances:
- Drugs, alcohol and poisonous substances.
- Glue, detergent and toilet cleaner.
- Harmful gases and volatile compounds.
- Traces of explosive and fire.
- Rubber and polymers.
- Petroleum products and hydrocarbon.
- Combustion powder and gunpowder.
- Soil and minerals.
- Based on traces/marks:
- Finger print and palm prints.
- Scars and wounds.
- Weight impression.
- Blunt force trauma.
- Stab wounds.
- Scratch mark on vehicle or human body.
- Drag mark on floor or carpet.
- Tyre mark and footprint or shoeprint.
- Bite mark, pinch mark or scratch.
The above examples are based on Lee (2012).
The physical evidence, the environment and issues:
When an investigating police officer manages to collect physical evidence from the scene of crime, there are questions that need to be answered. There are issues need to be considered. The questions can be as such (Case, 2011):
- In the case of fire involving a house or a factory, can the incident created to cover up any evidence to other crime such as murder?
- In the case of hanging, was it really a suicide case or it was portrayed as such to obscure the investigation?
- Are the wounds on the victims as similar as the weapon found at the scene? Can the wound be self-inflicted?
- In the case of burglary, was it really happened or it was done to claim the insurance?
- Are the fire started by someone or was it due to a short circuit? What is the source of origin?
- Are the wounds resulted from blunt or sharp weapon? Is the weapon found at the scene or with the suspect?
What can the evidence do?
An investigating police officer should consider all information related to a crime. It includes the testimony of witnesses and the victim, the suspect confession and video recorded by a closed-circuit camera. However, he will need strong physical evidence that will not be easy to be contradicted during trial.
Without obtaining relevant and sufficient physical evidence, the foundation of the case will be easy to be questioned by the counsel in court. If the physical evidence and related facts regarding the case were collected sufficiently by following the correct procedures, and were handled with absolute care, it will be the most accurate and useful evidence in the court of law.
Lee (2012) also describes some of the functions of physical evidence in supporting the investigation process. These functions are as follows:
- To determine the direction of the investigation in a criminal case.
By answering the questions that could guide the investigation, an investigator must determine the direction of his investigations based on evidence collected.
The physical evidence and the environment should be used to direct the investigation with more clarity and focus without prejudice and bias. A criminal case can be solved properly.
- To reveals the relationship between a crime scene to another scene and its relation to an identified suspect.
The famous Locard’s Theory confirmed the relationship between the crime scene to the victim and the perpetrators and the theory have done a good part in police investigations. With the discovery of relevance physical evidence, it can strengthen the police investigation.
Physical evidence such as strands of hair, semen, blood, saliva and bite marks on the body of a rape and murder victim; strengthen the investigation and help to focus on particular details. Even so, it does not mean that the scope of the investigation is reduced. It could be expanded depending on the case.
From the physical evidence collected, a lot of laboratory analyses can be conducted to test the reliability of the evidence to the case. Such analysis is DNA analysis; which can be used as the most powerful evidence recently as it is unique to each individual. Therefore, to gain such reliable results, they need reliable physical evidence too.
- To provide continuity between the testimony of the witness, the victim (if still alive) and also the suspects and to answer questions that was left behind.
After the evidence were analysed in the laboratory and results were produced, the investigating police officer could infer the validity of the evidence to the recorded testimony he got from the witness, the victim and the suspect.
Is the DNA from B could be detected in blood, in saliva from the bite marks and in semen collected from the victim’s vagina? If not, is the previous testimony valid and could be used as the evidence?
What if the DNA detected were came from more than one person? Is the crime committed by a single criminal or in a group? If in a group, how many of them involved?
The value of the evidence
However, the value of the physical evidence could be decreased and actually gone if the evidence was not handled properly to preserve the integrity. Integrity is an aspect that is critical when dealing with physical evidence. It should be treated properly by the investigating police officer and his team. The integrity of the evidence could only be confirmed when the chain of custody preserved.
The chain of custody can be preserved by ensuring that all the steps taken during the investigation (identification of the evidence, the collection, the storage and transportation to the laboratory, the analysis and reporting of the results) were recorded in clear and detail. Everything must be documented in systematic. Thus, the investigator can convince the court about the transparency of the investigation conducted to come to the relevant and accurate results.
There is no point bringing all the evidence from the smallest one such as a cotton swab smeared with blood stains to the mattress into the courtroom if the chain of custody is questionable. At the end of the day, all the hard work will be a waste as the evidence and the results of analyses could not be accepted in the court of law.
It is a loss to its solicitors whom have prepared a strong case against the accused. It is also a loss to the government as the spending in performing the scientific investigations requires a lot of money.
Once the evidence was analyzed, it will not give the same results if it is tested again. It will lead to more questions that may be raised by the defense counsel to prove any reasonable doubt.
Therefore, the physical evidence should be in the supervision of the personnel in-charged and recorded for each step or procedure performed. Only then, justice could be given to all parties involves.
Case, J.R. 2011. Chapter 2: Crime-Scene Investigation and Evidence Collection. http://www.school.cengage.com/forensicscience. Accessed: 15 January 2014.
Lee, S. 2012. JS 190: Physical Evidence and Biological Evidence. (Online posting). http://www.sjsu.edu/. Accessed: 15 January 2014.
UNODC. 2009. Crime Scene and Physical Evidence Awareness for Non-forensic Personnel. Vienna: United Nations Office on Drugs and Crime.
|Last Reviewed||:||17 March 2014|
|Writer||:||Norzita bt. Mohammed|
|Accreditor||:||Saravanakumar a/l Maniam|