WASHINGTON—Washington, D.C., prosecutors say a German man charged with killing his much-older journalist wife tried to enlist a drug dealer to "do away with her."

Prosecutors also say Albrecht Muth repeatedly threatened and assaulted Viola Drath in the years before she died at age 91. They want to use those assaults as evidence in Muth's upcoming murder trial in D.C. Superior Court.

The 48-year-old Muth is charged with first-degree murder in the August 2011 death of Drath, who was found strangled and beaten in a bathroom in the couple's Georgetown row home.

Court documents also show that the wife met with State Department agents who had been investigating her husband, who made fictitious claims of being an Iraqi army general. Muth's public defender didn't immediately return a phone message Tuesday.