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Investigating Insanity Cases: Part Two

March 15, 2021  By Peter Collins

My February 2021 column explored the legal definition, the myths and realities of the Not Criminally Responsible on Account of Mental Disorder (NCRMD). This month, we’ll discuss the investigatory aspects of these cases: crime scene considerations, interviewing the suspect, witness interviews, background investigation and information that should be obtained when the accused is in custody.

Crime Scene Considerations

Even without direct access to the suspect, the investigation into his state of mind can begin from a careful analysis of the crime scene(s) and from detailed interviews of those who may have witnessed some part of the crime.

Regarding the scene(s) of the crime, the following are important considerations:

  • Evidence of planning (e.g. bringing a weapon with him to facilitate the commission of the offence);
  • Cleverness of the crime;
  • Flight or escape from the scene;
  • Apparent focus to the commission of the offence;
  • Efforts to avoid any unintended victims;
  • Apparent preparation of the field in which the offence was committed;
  • Concealment of the scene and efforts to ensure privacy;
  • Destruction or attempted destruction of inculpatory evidence;
  • Steps taken to facilitate the crime (e.g. cutting telephone lines);
  • Operation of any of the base motives (e.g. lust, greed, envy, pride, revenge).

The observations of witnesses, especially as they relate to the demeanor of the offender, are often crucial in combating a claim of insanity and in establishing the existence of criminal intent. Did the offender appear to be oriented to time, place and situation? Were they able to communicate? Were they physically coordinated? Did they appear to be goal-oriented and focused?


If witnesses saw the suspect before the offence, ask if they observed any stressful event experienced by the offender preceding the crime. Witnesses to the crime, or events preceding or following the crime should be asked to comment on the suspect’s demeanour, speech, motor activity, orientation to his environment, emotional reactions, ideation, coherence, intelligence and judgement.

The Interview

As with any interview, preparation is the key. The more you know about the offender, his background and how he thinks, the better chance you have for a successful interview. To assist in determining the validity of the claim of a Not Criminally Responsible on Account of Mental Disorder (NCRMD) defence the following topics should be explored:

  • An awareness of his/her rights;
  • Planning;
  • Motive;
  • Intent;
  • Apparent rational acts prior to, during or after the crime;
  • Flight or escape;
  • Cleverness of the crime;
  • Apparent focus of the crime and efforts to avoid unintended victims;
  • Preparation of the “field” where the offence would occur;
  • Privacy or concealment;
  • Attempts to destroy/conceal evidence
  • Apparent normalcy of his life (e.g. job, friends, social life);
  • Deception of authorities, friends or family;
  • Use of false names;
  • Operation of any of the base motives;
  • Steps taken to facilitate the offence;
  • Knowledge that the act was a crime;
  • Knowledge that society sees the act as wrong, morally and legally;
  • Knowledge of consequences;
  • Long and short-term memory difficulties;
  • Medical conditions;
  • Stressful events before the crime
  • Use of alcohol or drugs;
  • Education and employment history.

Once the subject has been detained, correctional officers may assist in determining the state of mind of the accused. They can provide information similar to background witnesses such as demeanour, speech, judgment, motor activity, orientation, the presence of delusions, emotional reactions, coherence and knowledge, and whether they appear to be responding to auditory hallucinations. It’s important to gauge the detainee’s ability to conform to the rules and regulations of the setting and assess their overall hygiene, grooming and cleanliness, toilet habits, eating habits, their demeanour on visits and any participation in offered programs. Seemingly trivial matters can and does go a long way to satisfying whether the offender is not, was not and has never been not criminally responsible.

If required, reach out to your forensic interview experts (polygraph examiners) and seek the assistance of an investigative support unit (i.e. the Criminal Behaviour Analysis Section of the Ontario Provincial Police, the Behavioural Sciences Sections of the Royal Canadian Mounted or Police Sûreté du Québec). These behavioural experts can assist in understanding bizarre and shocking crimes by giving focus to the investigators, identifying areas that may be important but not obvious, and provide interview strategies.

In Conclusion

For the successful prosecution of a serious crime (or series of crimes), the prosecutor may have to deal with a claim that the subject was “insane” at the time of the offence. In order for the prosecution to effectively fulfill its function, the investigation of the crime and the criminal must be exhaustive and focused. The case, the skill to present the evidence in a manner that is easily understood, the expertise to effectively advocate for a particular result and the result that is called for by the evidence depends on it. Gathering evidence in a fashion that it will be admissible at the trial must be a collaborative effort between the investigators and the prosecutors. This combined effort of police and prosecutors will lead to the jury understanding the insanity defence. It also allows them to correctly decide whether or not the offender was not criminally responsible at the time of the offence.

Dr. Peter Collins is the operational forensic psychiatrist with the Ontario Provincial Police’s Criminal Behaviour Analysis Section. He is also a member of the crisis/hostage negotiation team of the Toronto Police Service Emergency Task Force. Dr. Collins’ opinions are his own. Contact him at

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