Criminal Investigation | The Canadian Encyclopedia


Criminal Investigation

Criminal investigation involves the investigation of violations of CRIMINAL LAW.

Criminal Investigation

Criminal investigation involves the investigation of violations of Criminal Law. In a criminal investigation, the state is responsible for all the expense of investigating the case and presenting it in court, with the exception of the accused's defence; however, if the accused is below a certain income level, the state will pay for a lawyer to defend him or her. This responsibility includes ensuring that all witnesses (prosecution and defence alike) appear at the trial. The victim of the criminal act is considered a witness and can be compelled to testify in almost all cases.

It is the state that decides whether a matter will proceed through the courts, and in making this determination it is not bound by the wishes of the victim or complainant. In contrast, in civil matters, the person who considers himself wronged must launch the action, secure his own witnesses, serve all processes and be responsible for the costs of the hearing.

The 2 processes differ also in the type of penalty handed down. In a criminal matter, convicted individuals either serve a term of imprisonment or pay a fine to the state, or both. In civil cases, there can be no imprisonment and the disputants may be ordered to pay to the offended party certain sums of money. Also, the evidentiary burden of proving guilt or innocence differs. In criminal matters proof must be beyond any reasonable doubt, whereas in civil cases the proof need only be on a balance of probabilities.

Constitutionally, the federal government is responsible for legislating in all areas that relate to criminal matters, while the various provinces are responsible for legislating in the areas of Policing and the administration of justice within their boundaries. Each province has passed a Police Act to meet these responsibilities.

Types of Crime

Historically, all crimes devolved either from a trespass against a person or a trespass against a person's property. Today the common terminology used is Crimes against Persons and Crimes Against Property. In recent generations the proliferation of crimes has been enormous, mainly because Canadian society has become so diversified and because so much material wealth has entered our lives. Today the distinction is less clear between person- and property-related crimes because of the growth of numerous so-called victimless crimes. Regarding victimless crimes, both the supplier and consumer of the illegal act are willing participants. Generally speaking, these types of crimes involve those having to do with the control of illegal drugs, sex and gambling.

The particular crime being investigated will, to a large degree, dictate the course that an investigation will follow; however, in order to convict all must meet the same evidentiary test - proof beyond any reasonable doubt that the accused intentionally committed the crime. Some crimes are planned and deliberate while others are spontaneous, unplanned acts. Crimes are variously motivated by greed, revenge, gain or pride. Some are committed by people suffering psychological abnormalities while others may be committed by exceptionally bright people. More often than not people who commit crime fall between these 2 extremes.


The purpose of a criminal investigation is to identify, gather and preserve evidence. Almost anything can constitute evidence, according to the particular circumstances of a case. The legal definition of evidence, all means by which a fact may be proved or disproved in a court of law, is of necessity very broad (see Law of Evidence). Evidence must be factual or based upon factual grounds. Opinion evidence is admissible, so long as the witness offering such evidence can satisfy the court that he or she qualifies as an expert on a specific matter.

Evidence can also be categorized by the forms it takes and the purpose it serves; eg, real objects, documents or testimony.

Almost anyone, including children, qualifies as a witness as long as they can offer useful evidence on the matter before the court. A witness, however, must meet the competency test. Testimonial evidence is that given by witnesses under oath at a trial. All evidence, including real and documentary forms, must be presented in testimonial form so that the opposite side has the opportunity to cross-examine on that evidence (see Law of Evidence for the admissibility test).

While there are statute and common-law rules of evidence and admissibility that have developed over the centuries, there is no one set way a peace officer must conduct an investigation. In other words, there are no statutory (or court) imposed procedural rules for the general investigation of crime.

A peace officer may question anyone believed able to offer useful information, but that person is not compelled to answer those questions. However, once a police officer has decided to charge persons with a criminal offence he or she must caution that person immediately that they are not required by law to answer any question put to them. The individuals must also be told without delay that they are entitled to call a lawyer for advice.

Evidence is also categorized by the purpose it serves. Evidence may be direct or circumstantial. Direct evidence is testimonial evidence of eyewitnesses to all or part of a crime. Circumstantial evidence supports one of the circumstances that form part of the overall picture of the crime.

An example would be as follows. A is poisoned by B and dies, but there are no eye-witnesses to the murder other than B, who cannot be forced to testify against himself. The investigation, however, reveals certain circumstances that implicate B in the murder; B was being blackmailed by A; B purchased an amount of the same type of poison found in the A's body; B's vehicle was seen in the area of A's home on the night of the murder. None of these facts alone would be sufficient to convict B of the murder, but their cumulative effect likely would.

Ingredients of Crimes

All crimes have essential ingredients, all of which must be proven beyond any reasonable doubt before an individual can be convicted. For example, the crime of possession of stolen property is composed of 4 essential ingredients: that the property was stolen by someone (not necessarily the accused); that the accused had possession of that property; that the accused knew that someone stole that property; and that the identity of the accused is known. The investigator must be aware of the ingredients of a crime before an investigation commences so that he or she can gather evidence to support each one.

Investigation of a Crime

Simply put, a criminal investigation is a search for witnesses and evidence to support the charge in court by proving beyond any reasonable doubt that the crime was committed and that it was the accused who committed it. It is critical to a successful investigation that the investigator(s) know the essential ingredients of the particular crime(s) they are investigating, otherwise they do not know what evidence to look for to support each of those crime's essential ingredients.

Crimes are either confrontational or discovery in nature. Assaults and sex crimes are examples of the former, car theft and fraud examples of the latter. The crime may be discovered by the victim, a witness or a peace officer.

Although there are various ranks within a police service, all are, by law, peace officers, with no one rank having greater legal power to investigate crime than another. The role of the peace officer is defined in section 2 of the Criminal Code of Canada. For instance, a chief of police has no more legal power than a rookie peace officer. Front-end uniformed peace officers are called constables in Canada. The type and severity of the crime, however, will dictate the rank and specialized knowledge of the investigating peace officer(s).

When a crime of any nature comes to the attention of the police, a constable will almost always be the first peace officer to respond. In the majority of cases, the original constable attending the scene will conduct the entire investigation but will call in whatever specialized help is needed. For example, in all cases of break-and-entry, theft of all types and common and aggravated assaults, the original constable will lead the investigation, even though higher-ranking peace officers assist. In other cases such as homicide and rape, the original constable will call out specialized peace officers (eg, homicide or sex crimes detectives) who will come to the scene of the crime and take over responsibility for the investigation from the outset. In such situations, these specialized people will bring in the specialized help they need, such as identification officers. In other types of crimes, the original constable will advance the investigation as far as possible, producing a written report which can be passed on to a specialized unit for followup investigation.

All peace officers are trained to attend to various aspects of the crime in sequence and order of importance, depending upon the particulars of the individual case. The normal order would be as follows: care for the physical needs of any person at the scene; arrest or identify the suspect(s); identify and locate witnesses; and secure whatever physical evidence is available at the scene.

For example, a constable responding to a robbery call at a convenience store sees the suspect flee. He chases and catches the suspect and finds an amount of money stuffed in his clothing which matches the amount stolen. There would be a clear power to arrest and charge the suspect on a charge of robbery and there would be no need for specialized help from detectives or other specialists; however, the constable would continue to investigate in a search for more evidence.

Conversely, if a constable were dispatched to a stabbing in a restaurant and on arrival finds the victim dead, the assailant gone and 2 people present who witnessed the stabbing, the constable would immediately call for specialized help and lock all doors to keep the crime scene intact and uncontaminated. He would also keep the witnesses at the scene until the homicide detectives and identification officers arrive. Upon the arrival of the specialized investigators, the constable would assist them in any way necessary, which would include writing a detailed account of all he did and witnessed.

As a rule, detectives and other specialists are trained to investigate 3 general categories of crimes; those that are very serious (eg, homicide or rape), those that are very complicated (eg, international drug dealings and white-collar crime), and those that require an extensive, protracted investigation.

Crimes are very often committed between people who know each other - eg, family violence, child abuse and sexual assault. History has shown in Canada that the majority of homicides each year occur between people who know each other. As a rule, these "acquaintance" crimes are easier to investigate and solve because there will be a starting point for the investigation.

Help from the community is absolutely critical to the apprehension and conviction of criminals but people are not required by law to assist their police. For this reason police need to work very closely with their community in a common effort to limit crime. However, if the police know the identity of a person who can offer useful evidence at a trial, that person may be compelled to testify. It is part of the civic duty shared by all to preserve the peace and prevent crime.

Physical evidence (eg, anything transferred from the victim or the scene to the assailant; anything transferred from the assailant to the victim or the scene), opportunity and motive are also crucial to a criminal investigation. An experienced detective will seek to understand the culprit's method of operation ("MO"). Successful investigators also build up a body of knowledge and expertise about those active in various types of crime in their community and they will also keep track on those people previously convicted but now on parole or probation.


It would be impossible to solve some crimes without the help of informants. Often the best informants are criminals themselves. The old adage "you have to be one to know one" fits very well here. An informant is one who either sells or gives information about a crime to the police. The most successful investigators are quite comfortable in the company of the criminal element because that is literally their workplace. Informants, however, include anyone who can provide any information about any crime; therefore, skilled investigators cultivate acquaintances with people who have extensive contacts with other people, such as taxi drivers, hotel desk clerks, apartment-building managers, etc.


Crimestoppers is a good example of police and community pulling together to fight crime. Most of the larger police services in Canada have well-advertised telephone numbers whereby people who wish to remain anonymous can provide information about crimes either free or in return for cash. For example, the Crimestoppers unit of the Edmonton Police Service is funded by the business community but staffed by police personnel. Each week those involved re-enact an unsolved crime and air it on local television and solicit telephone calls providing information about crime. Most informants are reluctant to testify at trial and generally will not be compelled to do so unless to prove the accused innocent.

Preservation of Evidence

All investigators must record and preserve evidence to ensure that it is available at trial and they must also be able to prove that the articles produced at trial are those that were seized at the time of the investigation. For example, in a narcotics trial, if continuity of possession by the investigator cannot be proved, the defence could allege that between the investigation and the trial there was a switch of substance, creating reasonable doubt about what exactly was taken from the accused.

It is critical that any victims' or witnesses' statements be written down as soon after the incident as possible, so that people may refresh their memories from these recorded statements prior to testifying. The investigator also records an account of the investigation as soon as possible.

Investigative Aids

Great strides have been made in recent years in the area of forensic science, pathology and other technological discoveries, but these technologies by themselves rarely get the job done. There are 2 recent cases in the US that demonstrate the need for both quality human evidence and quality scientific evidence. In the O.J. Simpson trial and acquittal of 1995, the amount of scientific and physical evidence available to the prosecution was compelling and should have been enough to convict - but it could not overcome the jury's distrust of members of the Los Angeles Police Department and their evidence. On the other hand, the Unabomber in the United States stymied for 18 years the most intensive criminal investigation ever conducted by the Federal Bureau of Investigation until they received an informal outside tip pointing them to Ted Kaczynski.

Identification Officers

Most police services either have their own identification specialists or have access to those of a neighbouring service. These people (often civilian) are specially trained in the various methods of evidence gathering, for example, fingerprints and photography.

Generally, these specialists are called upon by an investigator when there are no good witnesses to the crime available and the investigator has been unable to find sufficient evidence to identify a subject. In all cases of serious crime, their assistance will be used.

Search Warrants

Search warrants are required before police may search private residences, buildings or lands. As a general rule, a judge will issue a search warrant if reasonable grounds exist to believe that the described articles will be found in a described building or place involving a particular crime. Search warrants empower police to enter private dwellings or other private places, using force if necessary, for the purpose of searching for the articles named in the warrants. In some instances, searches of persons found on the premises are allowed. If evidence is found, it may be seized and held until the trial date.


It is clear from experience of the past half century that successful criminal investigators are fashioned not so much by physical fitness, training and education as by personal traits; eg, qualities such as curiosity, intuition, patience and the ability to judge people's characters and to analyse evidence. The emerging criminal investigator will soon learn that these qualities, rather than technical or legal skills learned in training, are crucial to criminal investigation. The best investigators also know that left to their own devices and working only within the knowledge and expertise of their police community, their success rates remain very low. Our police have learned in recent years that working alone they are relatively powerless in preventing or solving crime and that to the extent that they are helped by their community, so too will their success rate grow.

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