Expert cybercrime analysts for a convicted sex trafficker say evidence for some of the most shocking charges against him was tampered with and planted on storage drives that were supposed to be in secure FBI custody, according to court documents.

NXIVM sex cult founder Keith Raniere, 64, is serving a 120-year sentence at a federal prison in Tuscon, Arizona. Prosecutors said he recruited women and girls into a sex cult disguised as a self-help organization. He had an “inner circle” of “slaves” and “masters.” Some of the women branded Raniere’s initials on their bodies. Prosecutors allege he held a domestic servant captive in a room for nearly two years.

One survivor, India Oxenberg, told the FOX News True Crime Podcast she endured “dehumanizing” treatment, including “repeated molestation and rape” before she and her mother escaped the cult.

The FBI declined to comment when reached by Fox News Digital.

“In my 20 years serving as an FBI agent, I have never observed or claimed that an FBI employee tampered with evidence, digital or otherwise,” he wrote. “But in this case, I strongly believe the multiple, intentional alterations to the digital information I have discovered constitute evidence manipulation.”