Topeka ? A former Missouri city official accused of killing four family members in Kansas will be able to present evidence of a relationship between his wife and another woman.

Lawyers for 48-year-old James Kraig Kahler are expected to argue their client suffered a mental breakdown as a result of that relationship.

Kahler is charged with four counts of capital murder in the November 2009 shootings of his wife, Karen Kahler; their two teenage daughters, Emily and Lauren Kahler; and his wife’s grandmother, Dorothy Wight, at Wight’s Burlingame home.

Kahler’s wife had filed for divorce in January 2009 in Columbia, Mo., where he was working as a city utilities official.

A judge in Osage County District Court ruled for the defense Wednesday on the issue of the other-woman evidence. The trial is scheduled to start Aug. 8.