Inmate who claims to have murdered 93 women is 'most prolific serial killer in US history'

A man who claims to have murdered 93 women is the most prolific serial killer in US history, the FBI has said.

Crime analysts believe all of Samuel Little's confessions are credible, and officials have been able to verify 50 confessions so far.

Investigators also provided new information and details about five cases in Florida, Arkansas, Kentucky, Nevada and Louisiana, which Little has claimed but they have not yet verified.

In video interviews with police, Little calmly recalls the murders and seems to remember specific details - including what his alleged victims were wearing - and even seems to smile.

The FBI also provided 30 drawings of his victims that Little created.

Samuel Little recalled his apparent murders to police. Credit: AP

The 79-year-old is serving multiple life sentences in California and has been behind bars since 2012.

Little says he strangled his victims between 1970 and 2005, apart from one who he claims he killed by drowning her.

Many of his victims were originally deemed overdoses, or attributed to accidental or undetermined causes.

Some bodies were never found.

Samuel Little is serving multiple life sentences. Credit: AP

“For many years, Samuel Little believed he would not be caught because he thought no one was accounting for his victims,” said crime analyst Christie Palazzolo.

“Even though he is already in prison, the FBI believes it is important to seek justice for each victim—to close every case possible.”

The FBI has mapped out the dozens of unverified killings Little has claimed between 1971 and 1996, at locations spanning the entire breadth of the US.

The FBI has begun mapping out dozens of unverified killings Little has claimed. Credit: FBI

In video interviews with police, Little calmly recalls the murders and seems to remember specific details - including what his alleged victims were wearing - and even seems to smile.

In one interview Little describes a woman he strangled in 1993 – and how he rolled her down a slope on a desolate road.

“I heard a secondary road noise and that meant she was still rolling,” he said.

In another video, he described a victim he met in a New Orleans club in 1982 and who he said was the only victim he "ever killed by drowning".

“She was pretty," Little recalled.

"Light-colored, honey-brown skin,” he said with a smile.

“She was tall for a woman. Beautiful shape. And, uh, friendly.”