KANSAS CITY, Mo. (AP) — A southwest Missouri man who was convicted of murdering an elderly woman in 1991 is set to be executed this spring after five criminal trials, a rarity in death penalty cases, an expert said. Throughout his trials, which unfolded over more than a decade and featured a jailhouse informant and blood spatter evidence, Walter Barton, 64, has maintained his innocence, his attorney said. The Missouri Supreme Court on Tuesday set a May 19 execution date for Barton, who was convicted in the killing of Gladys Kuehler, 81, reported The Kansas City Star. She was found stabbed more than 50 times at a mobile home park she managed in Ozark, near Springfield. Barton went on trial five times from 1993 to 2006. Two ended in mistrials, one of which stemmed from a jury deadlocked over his guilt, and two of his convictions were overturned. His final trial, which ended in his third conviction, was before a Cass County jury. Robert Dunham, executive director of the