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Similar Act Evidence in Criminal Trials to Prove Identity of the Offender

In some situations there are many crimes committed by the same person.  The prosecutor only has a strong case establishing the identity in one of the incidents.  How does the prosecutor attempt to prove the other crimes?  The answer is similar act evidence applications.

The Prosecutor is generally not allowed to lead propensity evidence during a trial to prove an accused person committed the crime alleged.  In other words, a prosecutor can’t just show that the accused is the sort of person that would commit the crime alleged to establish the identity of the perpetrator.

Propensity reasoning is usually excluded from evidence because its prejudicial effect is seen to outweigh its probative value.  There is no doubt that this evidence is relevant.  It is a sound logical conclusion that past behaviour is the best predictor of future behaviour.   The difficulty in the courtroom setting is that society does not want people convicted just because they are the “type” of person to commit a certain crime.

Similar act evidence is admissible in court where the force of such evidence is so powerful that it can overcome the possible prejudice.

Similar act evidence is generally evidence that is relevant to an issue in establishing a design or in rebutting a possible defence.  The focus of this article is similar act evidence being used to establish identity.

Similar Act Evidence – Admissibility

Similar act evidence will only be admissible at a criminal trial if the Crown can establish that it is more likely that the probative value outweighs its prejudicial effect.

The Court will consider the following matters on similar act:

  1. The conduct that is the subject of the application. Is the conduct that of the accused?
  2. If so, is the proposed evidence relevant and material to the issue in the case?
  3. If relevant and material evidence, is it discreditable?
  4. Does the probative value outweigh the prejudicial effect?

Similar Act Evidence – To Prove Identity

In proving identity, similar act evidence, is generally excluded except where the evidence between acts is “strikingly similar” so that common sense dictates its inclusion.  The “strikingly similar” necessity prevents weak character type evidence coming before the court.  For example, if an accused had committed a home invasion in 1992.  The Crown two years later would not be able to use that home invasion to prove identity of the same accused in a new home invasion case unless there were other features present that made it “strikingly similar”.

In order for it to be strikingly similar there would have to be factors present that tended to narrow down the possible identity of the home invader.  Uniqueness to the way the crime occurred or was carried out is a way to get to the strikingly similar category.

Example of Strikingly Similar:

Imagine two bandits rob a family home in November of 2013.  One bandit gets cut in the process and leaves a trail of blood on the floor.  The second bandit drops his facemask at the scene. The robbery occurred in the desirable Forest Hill neighbourhood in Toronto at 3:00 a.m. Both bandits wore red one-piece Spandex outfits and black balaclava facemasks. The bandits tied up the family members, back to back with Duct tape, and told them that if they tried to escape before the bandits left the house that they would light their house on fire. The bandits poured gasoline all over the inside of the house.

The police recover DNA profiles from the blood on the floor in the house and the facemask left at the scene. The DNA matches two known criminals named Biff and Jimbo. Biff and Jimbo are arrested for robbery.

In August of 2013, another robbery occurred, in the posh enclave that is Forest Hill, where the victims were robbed in the early morning hours by two bandits wearing balaclavas and red one-piece Spandex outfits. The bandits tied up their victims with duct tape and poured gasoline all over the house. Threats were made of arson if the victims tried to escape before the Spandex-clad bandits left the house. No DNA was left behind.  The August 2013 home invasion robbery remained unsolved until Biff and Jimbo were arrested for the November of 2013 robbery.

In this example the police would charge Biff and Jimbo with both robberies once they determined the robberies were likely carried out by the same people. The November of 2013 case is very strong because of the DNA evidence left behind by the bandits Biff and Jimbo.  The DNA proves the identity of Biff and Jimbo as the bandits.

The August of 2013 case is weak, on its own, because there is no evidence that would identify Biff and Jimbo as the Spandex-clad bandits.  The prosecutor would then use similar act evidence to establish the identity of Biff and Jimbo as the perpetrators of the August 2013 home invasion robbery based on the fact that the two robberies are “strikingly similar” and the identity of the bandits is known for the November of 2013 robbery.  The prosecutor would argue it is beyond the scope of mere coincidence that both robberies were conducted by different individuals.


As you can see, similar act evidence can be a powerful tool in establishing the identity of an offender.  The judges and courts must be cautious to guard against wrongful convictions and therefore should not be overly comfortable with admitting this evidence into trials.

A criminal defence lawyer in Toronto could oppose the admission of similar act evidence, conduct cross examinations and call other evidence to rebut the prosecutor’s theory of similar acts being committed by the same individuals.

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