The Federal Bureau of Investigations (FBI) has designated a man who has confessed to nearly 100 murders and is serving multiple life sentences in a California prison as the most prolific serial killer in the history of the United States.

The now 79-year-old Samuel Little who has been in prison since 2012 for the murders of three women told detectives last year that he had killed 90 more across the US between 1970 and 2005.

The FBI have said that crime analysts and investigators believe that all Little’s confessions were credible, with 50 of them so far verified, making him the most prolific serial killer in US history.

Little told investigators that he strangled most of his 93 victims, many of whom were black women. Many of his victims have never been found and his crimes are still being investigated by the FBI.

Earlier in the year, detailed pictures drawn by Little himself emerged, thought to be of women that he murdered.

Although the exact time of when Little drew the pictures has yet to be ascertained, the FBI said they were based on his memories of some of his victims.

In videos released by the FBI, Little described in detail a number of the women he claims to have murdered whilst he was at large, helping the Police to link his confessions to victims.

It took years to catch Little, partly due to his nomadic lifestyle where he moved from place to place, targeting vulnerable women most of whom were on the fringes of society, such as drug users or sex workers.

Little’s confessions also mean that he has overtaken Gary Ridgway, otherwise known as Green River Killer in terms of number of people murdered in the US.

Ridgway was convicted of 49 murders in 2004 and sentenced to life imprisonment in Washington State Penitentiary.

It also makes him more prolific than the infamous Ted Bundy, who confessed to killing more than 30 women in the 60s and 70s before his execution in 1989.

His killing sprees also shadowed that of John Wayne Gacy, known as the Killer Clown who also confessed to more than 30 murders, mostly young boys before he was executed in 1994.