During a lawsuit challenging the US state of Michigan’s ban on same-sex marriage, a witness for its defence has been banned from testifying.

Sherif Girgis, a Yale University law student, who has written extensively on historical defences of marriage between one woman and one man, and had been slated to appear in court in defence of the state’s same-sex marriage ban.

However, he was on Monday dismissed by Federal Judge Bernard Friedman, who said Girgis’ opinions will not help him decide in this case.

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

The state Attorney General’s office is to call a break in order to call a replacement witness.