BEDFORD, Va. (AP) — A lawyer for a convicted sex offender who pleaded guilty to felony murder in the 1975 deaths of two young Maryland sisters says the man insists he didn’t sexually assault or kill the girls.

Lloyd Lee Welch Jr. entered guilty pleas Tuesday to two counts of first-degree felony murder. That crime is defined as a killing that occurs during the commission of a felony. In this case, the girls were killed after being kidnapped from a shopping center in Wheaton, Maryland.

Under a plea agreement with prosecutors, Welch admitted that he participated in the abduction of the girls, but continued to deny that he participated in their sexual assault or in their killings. Prosecutors have named other members of Lloyd’s family as persons of interest, but have not charged anyone else in the case.

Prosecutor Wes Nance said Welch’s credibility is “open for questioning.” Nance said Welch’s account of who was involved in the girls’ abduction, sexual assault and killing changed repeatedly during interviews with police over the last several years.