OLYMPIA, Wash.—The Washington Legislature passed a measure March 4 to expand the state’s domestic partnership law, granting same-sex couples more than 170 of the benefits and responsibilities given to married couples, including property and guardianship rights.

The Senate gave final approval on a 29-20 vote after minimal debate. The bill now goes to Gov. Chris Gregoire, who is expected to sign it.

The measure adds domestic partners to sections of laws where previously only spouses were mentioned, including areas referring to probate and trusts, community property and homestead exemptions, and guardianship and powers of attorney.

The underlying domestic partnership law, passed last year, already provides hospital visitation rights, the ability to authorize autopsies and organ donations and inheritance rights when there is no will.

More than 3,500 couples have registered as domestic partners since the law took effect last year.

The measure makes dozens of changes to state law, including requiring domestic partners of public officials to submit financial disclosure forms, just as the spouses of heterosexual officials do.

It also would give domestic partners the same spousal testimony rights that married couples have, allowing domestic partners the right to refuse to testify against each other in court.