The Supreme Court of Canada upheld the amendments made by the Liberals to the rape shield laws in Canada four years ago.

In a 6-3 ruling issued today, the court said the expanded rules preventing the use of the complainant's past against sexual assault in trial are "constitutional as a whole."

Rape shield laws were enacted four decades ago to prevent complainants in sexual assault cases from having their sexual history introduced as evidence.

The criminal law states that evidence of the complainant's prior sexual activities unrelated to the charges cannot be admitted except with the judge's permission after a special hearing, and cannot be used to infer that the complainant is less credible.

In 2018, the Liberals expanded the definition of such evidence to include sexually explicit communications like emails and videos, as well as documents about the complainant in the possession of the accused.

They also granted the complainant the right to participate in the screening hearing with the judge and to be represented by a lawyer there.

In today's ruling, the majority of justices say the right to a fair trial does not guarantee the accused "the best possible trial" and that "setting a trap for complainants with their highly private records" can be unfair and unhelpful in the search for truth.