Jurors in the US trial of a middle-aged German man charged with killing his 91-year-old wife were shown bloody crime-scene photographs and a portion of an interview with homicide detectives in which he referred to the couple's relationship as a "marriage of convenience". Albrecht Muth, 49, also describes how he found the lifeless body of his wife, Viola Drath, in a bathroom of their home in Georgetown, a posh Washington neighbourhood, but decided that it would be futile to try to resuscitate her. "The obvious was obvious," Muth told the pair of homicide detectives. Muth is charged with the first-degree murder of Drath, a German journalist and socialite, who was found beaten and strangled in August 2011. He faces life in prison if convicted. Muth's lawyers say he's innocent. Prosecutors, meanwhile, say Muth lived off a monthly allowance from his wife that had recently been reduced. In video shown to jurors, one of the detectives asks whether the couple was intimate. Muth replies: "We had a marriage of convenience." Prosecutors presented photographs of Drath sprawled dead on the bathroom floor. A large, bloody gash covered her neck, another wound was found on the back of her neck and a fingernail had been nearly ripped off.