Killen, the owner of a local sawmill and a former unsuccessful candidate for sheriff, was a marginal character until Sam Bowers appointed him "kleagle," or klavern recruiter and organizer, for the Neshoba and Lauderdale County klan. He zealously performed his duties, as evidenced by the over seventy men who met on June 16 in Meridian to plan a trip to Mount Zion Church in Longdale, where they hoped to find and kill Schwerner. Instead of encountering Schwerner, they found only local blacks, who the klan badly beat before burning down their church.
After Killen received word from Price that Schwerner and the other two civil rights workers were being held in jail, he travelled to Meridian in Lauderdale County to meet with other klan bigwigs at the Longhorn Drive-In. Phone calls were made and recruits signed up for a trip that evening to Neshoba County. A larger group of Klan met at Akin's Mobile Homes in Meridian, where Killen informed them of the plan he had worked out with Price for the three men's release shortly after dark. He told klan members participating in the murderous expedition to get rubber gloves. A meeting was scheduled near the courthouse in Philadelphia for 8:15. When the Meridian klan arrived in Philadelphia, Killen took them on a driveby tour of the jail that held their quarry, then rushed off to establish his alibi by attending a wake for an uncle at the local funeral home.
The FBI was informed of Killen's role in the conspiracy by informant Wallace Miller, Killen's first klan recruit. Killen was one of nineteen men arrested on December 4, 1964. At his trial in 1967, Killen created a stir by passing to his defense attorney a question for a prosecution witness, Reverand Charles Johnson. His attorney then asked the question in cross-examination. Is it true, Killen asked, that Johnson and Michael Schwerner had tried to "get young Negro males to sign statements that they would rape one white woman a week during the hot summer of 1964 here in Mississippi?" The judge was not amused by the question, and demanded to know where it came from.
The jury was unable to reach a verdict on Killen's guilt.
In June 2005, Killen was retried on state charges. Judge Marcus Gordon Killen to serve three 20-year terms, one for each conviction of manslaughter in connection with the deaths of Chaney, Goodman, and Schwerner in 1964. Judge Gordon said in pronouncing sentence, "I have taken into consideration that there are three lives in this case and that the three lives should be absolutely respected." Sentencing followed Killen's conviction earlier in the week. The manslaughter convictions came after nearly three days of jury deliberations. The jury found that there was reasonable doubt as to whether Killen intended that the klansmen kill the civil rights workers, and thus did not return a murder conviction.