The Canadian Review of Policing Research (2004)

ISSN: 1710 6915


Dianne L. Martin

Dianne Martin teaches criminal law at Osgoode Hall Law School, York University, Toronto. She is associated with the Innocence Project, where cases in which the convict continues to assert innocence are re-examined by law students. The summary is taken from “Lessons about Justice from the ‘Laboratory’ Of Wrongful Convictions: Tunnel Vision, The Construction Of Guilt And Informer Evidence”, University of Missouri-Kansas City Law Review, 70:4, 847-864.


This short article considers the phenomenon of “tunnel vision”, or “investigator bias”, as it has been demonstrated in the scores of wrongful conviction cases that have come to light in recent years. It discusses three ways in which tunnel vision is operationalized by police investigators and contributes to miscarriages of justice: note-taking, testimony at evidentiary hearings, and the use of informer evidence, particularly the evidence of in-custody or “jailhouse” informers. The article concludes that the procedural reforms proposed to respond to the acknowledged risks associated with reliance on jailhouse informer evidence are likely to be inadequate.


The article draws on earlier research on the police role in wrongful convictions,1 as well as case law and literature dealing with police note-taking and testimony, and the recent public inquiries into wrongful convictions such as those of Guy Paul Morin in Ontario and Thomas Sophonow in Manitoba.


Cases of wrongful conviction have been identified with increasing frequency in recent years, throughout the common law world, and have fuelled considerable research and concern from both the academy and government. It is now apparent that wrongful convictions are not a matter of inevitable human error, regrettable but exceptional. Rather, systemic factors which occur in all jurisdictions and in various types of cases are identifiable. Most known cases of wrongful conviction have resulted from a pressure on law enforcement officials to resolve the case either because it is high profile or because of resource or other institutional factors. That pressure in turn triggers and justifies a bias known in the literature on wrongful conviction as “tunnel vision”, which is a set of preconceptions and heuristics that causes police investigators to select evidence to build a case for the conviction of their chosen suspect while suppressing or ignoring information and interpretations that point away from guilt.

The result is an adverse impact on the reliability of virtually all phases of an investigation. The adverse impact has been evident primarily in the hundreds of high-profile cases of wrongful conviction that have been identified to date. But there is no reason to believe that these are the only cases where this type of investigation has produced a miscarriage of justice. Less notorious or less serious cases may be even more vulnerable to investigative shortcuts and bias. The phenomenon of tunnel vision may be responsible for miscarriages of justice in cases where innocent people plead guilty or are convicted after trial, and where innocent people acquitted after being wrongly accused nonetheless suffer from the stigma and disruption of being charged and tried.

The Construction of Convictions

Criminal convictions are a social product, the result of numerous choices and decisions by investigators about the relevance and reliability of information and witnesses. When the investigative process is distorted by tunnel vision, misconduct becomes prevalent in note and record keeping, witness interviews, the interrogation of suspects, and the conduct of searches. This leads to the presentation at trial of incomplete or even entirely inaccurate evidence, and to a dramatic increase in the risk of miscarriages of justice. Two examples illustrate the process, the police notebook, and police testimony on evidence admissibility hearings.

1. The Police Notebook

The notes that police officers make about their activities serve a number of purposes, not the least of which is to provide officers with an ‘aide memoir’ to assist them when giving evidence. The notes lend precision and detail to police officers’ testimony and tend to enhance their credibility, particularly in contrast with the accused. There is some evidence that on-the-job training in note writing begins early, as it is well understood that a consistent version from all officers involved in an event is an important factor in obtaining convictions or other desired outcomes.

There is a body of case law specifically criticizing the practice of officers collaborating after an event in the preparation of notes, rather than making contemporaneous notes based only on their own observations. Some judges have been concerned by this practice and the suspicion it supports that inconsistencies are being deliberately eliminated. However, other courts have been less concerned, and commentators have expressed the view that even legislation setting out proper practice for note-taking would have little effect on the tendency of courts to accept police testimony.

2. Evidentiary Hearings

Hearings on the admissibility of statements given to the police by accused persons and sought to be used in court as confession evidence, and the propriety of search warrants and search practices, are almost entirely decided on police testimony. Such hearings are thus the occasion for strongly argued contests over police credibility. Courts have gradually moved from indirect criticism of the quality of evidence presented in support of the police position (that the interrogation was conducted or the evidence was obtained lawfully) to requiring police to provide an objective record of the interrogation or other investigative practice. In the context of confession evidence in particular, the courts are beginning to insist on receiving an objective (understood to mean “electronic”) record of the interrogation to prove that the statement was given voluntarily. It is now becoming better understood that police officers regard the law as a tool and, with respect to confession evidence for example, they have consistently interpreted court decisions on the conduct of interrogations as a testimonial challenge rather than a guide to changing their investigative practices.

Many factors have influenced the evolution of judicial attitudes towards police testimony on evidentiary hearings. One of the most influential, in the United Kingdom at least, was learning that the men and women convicted of the IRA pub bombings in the 1970’s were innocent. Their so-called confessions were the product of police coercion and perjury, and their false confessions provide classic illustrations of the phenomenon of the false confession, as well as the judicial deference toward police testimony that facilitates police misconduct. One of the most infamous examples of the latter is found in the ruling that dismissed a civil action by wrongfully convicted prisoners trying to prove that their confessions were false and had been obtained through coercion. Lord Denning noted that to allow a lawsuit against the police to continue would suggest that it was possible that the police had lied and put innocent men behind bars. He described this possibility as “an appalling vista” that he would not countenance.

Informers and Wrongful Convictions

Much police work relies on informers, whether in the sense of the person who reports a crime, or in the more commonly used sense of one who provides information to the police in exchange for some benefit. Informer evidence always carries risks, whether the informers are developed by police or come forward of their own initiative. Both circumstances are seen in the wrongful conviction cases. Tunnel vision magnifies the risks.

1. Developing Informers

In the IRA pub bombing cases in England, police rounded up hundreds of Irish men and women who had any possible connection with the IRA and subjected them to intense interrogation until they obtained names and information. Britain’s anti-terrorism laws permitted abusive interrogations and lengthy detention of persons who might provide information. The men and women ultimately charged as a result of this process were convicted. All were innocent but were not freed and exonerated until they had spent up to seventeen years in prison.

In Canada, the wrongful convictions of Donald Marshall, junior, and David Milgaard were both obtained through the false testimony of youthful informers, pressured by police to give evidence that was only shown to be false years later.

2. Jailhouse Informers

So-called jailhouse informers, or prisoners who claim to have heard a confession from a (usually high profile) suspect and testify against the suspect in exchange for some benefit, are notoriously unreliable. Because of tunnel vision their testimony continues to be implicated in wrongful convictions, such as that of Guy Paul Morin and Thomas Sophonow. Judicial inquiries in Canada and elsewhere recommend strongly against their use.

Conclusions and Implications

The safeguards such as stringent limits on the use of jailhouse informers being introduced to reduce wrongful convictions may not be sufficient, particularly if the criminal justice system continues to be distorted by myths about its fairness and its leniency. Nor will these safeguards address the pressures that high-profile cases generate, or the political and other benefits that accrue to those who resolve them, whether accurately or not.


1. Dianne L. Martin, “The Police Role in Wrongful Convictions: An International Comparative Study” in Saundra Westervelt and John Humphreys, eds., Wrongfully Convicted: When Justice Fails, Piscataway, New Jersey: 2001, Rutgers University Press.