Judge Marcus Gordon said he saw no reason to reduce the sentence because the former Ku Klux Klan leader is 80 years old. It took 40 years for prosecutors to bring the case.
Killen received 20 years on each of three counts of manslaughter to be served consecutively. Gordon said had the sentences been imposed in 1964 no one would have said the sentence was excessive.
"I've been a judge for 26 years," Gordon said. "I've never really learned how to do it (sentencing). I've just done what I thought was the best thing to do."
Killen was convicted of manslaughter Tuesday in the deaths of James Chaney, Andrew Goodman and Michael Schwerner, who were beaten and killed June 21, 1964. The incident became the basis of the movie, "Mississippi Burning."
The jury had the choice of convicting him of murder but opted for the lesser charge.