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This string of text could fit into a tweet with room to spare. But it brings an end to a common-law tradition, going back at least 400 years, of “spousal immunity” in criminal trials. Your husband or wife can now be compelled to testify against you concerning any funny business you have gotten up to — although communications made between parties to a marriage are still privileged and sacrosanct. (Your Mr. or Mrs. can be forced to say what he or she saw you do, but not what you said about it.)

The principle of spousal immunity was one of those rules of criminal law of which most everybody has a vague popular understanding from movies and TV shows. Like most such rules, it had already been shot through with many lesser-known holes. Blackstone’s Commentaries (1769) describe the primordial rationale for spousal immunity. “By marriage,” he declares, “the husband and wife are one person in law.”

“In trials of any sort,” he adds, “they are not allowed to be evidence for, or against, each other: partly because it is impossible their testimony should be indifferent; but principally because of the union of person.” Already, though, there was a recognized exception: “where the offence is directly against the person of the wife, this rule has been usually dispensed with.”

Earlier changes to the Canada Evidence Act allowed spouses to call one another as witnesses in their own defence, and removed spousal immunity altogether for particular offences, notably sexual assaults of children. The provinces individually did away with spousal immunity in civil trials. And the Supreme Court eventually removed it in cases of husbands and wives who were “separated with no reasonable prospect of reconciliation.”