Currently, under the Canada Evidence Act, spouses can refuse to testify against their partners except in certain specific cases such as sexual assaults or those involving children.
Legislation introduced last week by the Harper government would remove that right.
MacKay defended the move Monday at a victims of crime conference in Ottawa, calling the provision outdated.
He said courts need to compel testimony from all witnesses of crime, including spouses.
"We do not feel that spousal immunity should present an obstacle to bringing important evidence before a court of competent jurisdiction," said MacKay.
"We feel that in cases of murder, in cases of terrorism, serious fraud, if a spouse has important evidence that the court needs to consider, that evidence should be there."
Some lawyers have predicted the measure will little impact on a system where spousal testimony comes into play in relatively few cases.
The proposed new Canadian Victims Bill of Rights would also allow witnesses to testify anonymously in certain cases.
Critics complaint that such a provision goes against the constitutional right of a person charged with a crime to face their accuser.
But MacKay said he has no problem with removing that right if it protects victims, particularly children or victims of sexual crimes.
"Not if it prevents further victimization," he said.
"And we feel on balance that courts, judges, will be in a position to weigh that consideration carefully."
The changes are part of a sweeping government bill that codifies the rights of victims.
Under the new provisions included in Bill C-32, victims will be able to request a copy of a bail order, a probation order or the details of a conditional release.
Victims will also have the right to have the courts consider making a restitution order in all cases and to have such orders registered as a civil court judgment against the offender if the money isn’t paid.
The federal Conservatives have long complained that the justice system places too much emphasis on the rights of the accused, rather than the people impacted by crimes.
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