An important trial begins Tuesday involving same-sex marriage in Michigan.

One of the key issues of the trail is regarding the rights of same-sex couples when it comes to adopting children.

A couple filed the lawsuit after finding out they were unable to adopt children together because of Michigan’s Defense of Marriage Act.

Related story: Couple fights Michigan ban on same-sex adoptions

In 2004, the state of Michigan enacted the Defense of Marriage Act after it was passed by 59 percent of voters.

This act argues that children benefit from living in homes of heterosexual couples.

The state is presenting four expert witnesses to testify on the emotional and social outcomes of children raised in same-sex households. 

The trial will be the first of its kind to include scientific studies on same-sex parenting. 

A decision is expected to be made after eight days of testimony.

Related story: Michigan State studies health of same-sex couples