A court challenge to Michigan’s same-sex marriage ban wrapped up on Friday with a Harvard University professor, an expert on marriage in the US.

Nancy Cott testified on Friday in a federal court in Detroit.

The lawsuit challenges a 2004 voter-approved ban on same-sex marriage.

The challenge is brought by two Detroit nurses who say it violates the US Constitution.

Starting on Monday, the Attorney General’s office will call witnesses in its defence of the ban.