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Evidence collection

Last edited: December 30, 2011

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In an investigation of domestic violence, sexual assault or rape, police need to collect a range of physical and verbal forms of evidence. In addition to taking statements from victims and suspects and documenting other verbal remarks or communication made by survivors or perpetrators during the investigation process, physical evidence, including forensic evidence of a crime (e.g. fingerprints, saliva, blood, and semen, tissue under fingernails, unique ligatures, hairs and fibres) – which is scientifically examined, should be collected. This evidence may prove vital in linking a perpetrator to a particular crime scene or victim.  

Key forms of evidence include:

  • Signs of injuries (e.g. cuts, scrapes, bruises, fractures, choking, pulled out hair) that can be photographed or attested to by an examining physician or medical clinician. Police should also be familiar with injuries that may not be visible immediately after an incident (e.g. strangulation, which may not appear for several days).

  • Torn clothing

  • Broken fingernails

  • Forensic evidence / DNA (e.g. fingerprints, saliva, blood, and semen, tissue under fingernails, unique ligatures, hairs and fibres; and in cases of murder, the victim’s body)

  • Paper documentation— diaries, letters, notes —either from the suspect or written by the victim and detailing past acts of abuse and violence

  • Weapons

  • Broken household items, indicating a violent incident

  • Observations of neighbours, friends and family

  • Statements from service providers involved in past incidents of violence

  • Prior police incident reports

  • Medical files detailing past injuries (used only with the permission of the victim)

  • Evidence of court orders, including bail restrictions or restraining orders

  • Evidence of alcohol and/or drug abuse by the offender

  • Criminal record/history of the alleged offender and all suspects

  • Computer, internet/ email, text messages, and other forms of electronic evidence (voicemails, answering machine tapes, emergency number police tapes)

Excerpt from: UNODC. 2010. Handbook on effective Police responses to violence against women. UNODC. Vienna.

The following considerations should guide evidence collection practices:

  • Forensic and medical examination should be made available to survivors, without requiring additional consent (such as from a male relative), whether or not they are choosing to make a police report.

  • Multiple collections of forensic and medical should be prevented to limit secondary victimization.

  • Forensic and medical evidence should not be mandatory to convict a perpetrator.

  • It is the survivor’s right to choose whether and how she wants to submit evidence and prosecution should be able to take place in the absence of the survivor.

  • Each item must be carefully collected, preserved and individually documented.

  • Evidence collection practices (including what should be collected and how to collect it) should be regularly reviewed and updated as needed through periodic meetings with prosecutors and other legal personnel.

(UNODC, 2010, United Nations -DAW/UNODC, 2010)


Promising Practice:
The Royal Canadian Mounted Police’s Domestic Violence Investigation Guide

The Royal Canadian Mounted Police in British Columbia has developed a Domestic Violence Investigation Guide, which directs police in gathering information for risk assessment and preparing evidence for prosecution. The guide aims to assist with the bail hearing by providing relevant information to the courts and to assist in identifying risk factors that may put the victim at further risk of violence. The information collected relates to both the suspect and the victim and includes full details on:

  • Suspect’s criminal history of violence

  • Suspect’s previous history of domestic violence

  • Court orders pertaining to the suspect and any history of violating such orders

  • Suspect’s history of alcohol/drug abuse

  • Suspect’s history of employment instability or financial problems

  • Suspect’s history of mental illness

  • Suspect’s history of attempted or threatened suicide

  • Suspect’s access to, use of or threat to use weapons

  • Victim’s perception of personal safety

  • Victim’s perception of future violence, or risk of violence

  • Current status of the domestic relationship (e.g. pending divorce)

  • History of escalation of abuse/violence in the relationship

  • If children are involved, have been or could be exposed to violence

  • History of threats by the suspect to the victim, her family, friends, co-workers or a pet

  • History of suspect forcing sexual contact on the victim

  • History of suspect displaying jealous behaviours, stalking or harassment of the victim or a previous partner

  • Other information that may be relevant (e.g. is the victim socially or geographically isolated, unwilling/unable to leave the home, does not speak the local language (a recent immigrant), living with some form of disability?)

Excerpt from: United Nations Office on Drugs and Crime, (2010), Handbook on Effective Police Responses to Violence against Women’, Criminal Justice Handbook Series, Vienna: UNODC; Royal Canadian Mounted Police.

Additional examples of guidance developed by police forces on how to investigate violence against women and girls, search the Secretary-General’s Database on Violence against Women and Girls (filter for Regulations/protocols/guidelines and police).