Available translations:
Available translations: English العربيّة

Collecting physical evidence

Graphic: Investigators collect evidence from a grave


  1. The investigator needs to consider what physical evidence may exist that is relevant to the case.
  2. NHRIs may need to seek expert assistance when collecting and storing physical evidence.
  3. Collecting evidence at a scene requires planning and specialised skills.

Physical evidence is anything tangible – that is, anything that can be touched or held – that may have some relevance to the investigation. It could be a sample of earth from the banks of a polluted river. It might be a computer hard drive or the SIM card from a mobile phone. It could be cartridge cases found at the site of a mass grave or a fragment of a bone. If it is relevant to the issue being investigated, it is evidence.

HOW IMPORTANT IS PHYSICAL EVIDENCE?

Physical evidence is very important to certain human rights investigations, particularly when they intersect with criminal investigations. Physical evidence is often crucial to investigations involving extra-judicial killings, torture, police brutality, systemic rape and similar allegations.

Physical evidence may not be as relevant in other types of human rights investigations, such as those focused on issues involving economic, social and cultural rights. However, there may be exceptions. For example, an investigation into pollution that is allegedly destroying economic livelihoods in certain communities may well involve the collection and forensic analysis of physical evidence.

WHAT SHOULD INVESTIGATORS KNOW ABOUT PHYSICAL EVIDENCE?

NHRI investigators should consider the possible existence of physical evidence as they plan and carry out their investigation. There may also be occasions when investigators:

  • Are given physical evidence
  • Go to a scene and discover previously uncollected physical evidence
  • Realise that unless they secure physical evidence, it may be destroyed, removed or contaminated.

While NHRI investigators may rarely have to collect physical evidence or submit it for forensic examination, there is always the possibility that this might be required. It is important to seek expert assistance in collecting physical evidence, if at all possible.


Graphic: An investigator bags a gun at a scene


ENSURING THE INTEGRITY OF PHYSICAL EVIDENCE COLLECTED

  • Take photographs and video everything as you find it.
  • Prepare a detailed diagram of the scene.
  • Measure distances to record the scale of the scene and the relative position of different items of evidence.
  • Always wear gloves when touching or handling an item.
  • Bag any item that may be relevant – one item at a time – and seal the bag.
  • Do not put items together in the same bag.

SECURING PHYSICAL EVIDENCE

Physical evidence should be identified and secured as quickly as possible. Most physical evidence is perishable, to some extent. It can be deliberately or naturally destroyed or contaminated.

Ideally, each item of potential evidence should be bagged and sealed, using a unique seal number. Sealing the evidence in a bag preserves the item for any forensic testing that may be necessary. 'Bagging and tagging', as it is sometimes known, should be done by an investigator who has received training in how to collect and preserve evidence.

It is very important to take photographs and video of physical evidence before it is moved. It should also be mapped and diagrammed, preferably using GPS technology.

Physical evidence should be preserved in a way that keeps it as close as possible to the condition it was in when it was found.


Graphic: Tape marks off a crime scene being investigated

COLLECTING EVIDENCE AT SCENES

A scene is a place where something happened. It may contain valuable physical evidence, even if time has passed since the incident under investigation occurred.

Processing a scene means examining it in a methodical fashion to minimise the possibility of evidence being overlooked. Processing should be done in a way that avoids destroying or changing any physical evidence.

The first task is to protect the scene from contamination. That includes limiting who can enter the scene and, if it is outdoors, protecting it from the elements.

Persons trained in scene processing will often work with the lead investigator to create a crime scene investigation plan. The plan will describe the area to be searched, what is being looked for and the order in which evidence will be collected

A scene should be photographed and videoed before anything is moved. It should also be measured, preferably using GPS technology.

A scene can also be processed using grid search methods. This is where the scene is divided into a grid, with each segment thoroughly searched for possible evidence.

NHRI investigators usually need expert help to process a scene to ensure that they do not miss crucial evidence or collect it in a way that leaves it compromised. For example, exhuming bodies from a mass grave may involve a variety of experts, including forensic pathologists, anthropologists and entomologists.



Image credits

  1. Investigators collect evidence from a grave - National Human Rights Commission of Nepal
  2. An investigator bags a gun at a scene - EUPOL Afghanistan Media, Flickr CC
  3. Tape marks off a crime scene being investigated - Null Value, Flickr CC