Robert Wirth was born in 1960 and lived in Milwaukee, Wisconsin.
In 1988 elderly women were being killed in their homes in the city at the rate of about one a week, and the police had no idea who was responsible. There were also burglaries in the same districts, and the prosecution was later able to put those before the jury as other-acts evidence, because the method of entry and the way the houses had been turned over were almost identical.
The cause of death was established by autopsy rather than assumed. Three medical examiners reviewed all the autopsy protocols and concluded that one man was responsible for the three homicides, on the basis of the injuries: each of the women had suffered a complete avulsion of the voice box, and the examiners thought the necks had been stamped on. They died of asphyxiation. The internal and external injuries were distinctive enough for the three examiners to attribute all three deaths to the same person.
There were no suspects at all. What broke it was a child's toy. At one of the scenes a detective noticed a toy donkey sitting on the couch, and when a member of the family arrived she said it did not belong there: it belonged on a chair, where the body had been found. The detective picked it up, turned it over and saw fresh blood smears. It went straight to the Wisconsin State Crime Laboratory, which established that the blood was not the victim's. Because it was fresh, the investigators believed it was the killer's.
Months later Wirth robbed a taxi driver. The driver fought him, took the gun away from him, and when the police checked the weapon they found it had been stolen from a house next door to one of the victims.
They then obtained his blood through a John Doe proceeding, and matched it to the blood on the toy. The case was made before DNA testing was routine. Conventional ABO enzyme markers gave a figure of one in four thousand five hundred and sixty-five. A DQ alpha test, then the only PCR marker available, was run in California and matched. Gamma and kappa markers were run in Minneapolis. Further work produced four RFLP markers, and the most conservative combined figure put the match at one in eight hundred thousand. The prosecutor said afterwards that in that era a figure of one in a thousand was considered a terrific case, and that he doubted the earlier numbers alone would have satisfied a jury, since the blood was the only evidence they had.
The trial lasted six weeks with the jury sequestered, and the conviction rested largely on the genetic evidence. He was sentenced in 1991 to four consecutive life terms plus twenty years.
Two things about the numbers. The prosecution account describes three homicides tried together, while the recorded disposition is four life sentences, and nothing accessible reconciles those. And the figure of six to eight comes from a reference work that gives no particulars for the additional deaths; the three described above are the ones the evidence was built on.
The account of the investigation here comes from a talk given by the prosecutor at a forensic science conference, which is the only substantial source on the case. No victim is named in it except Mrs Bresnahan, whose scene produced the toy.