His drawings include details such as the color of the eyes and hair of the victims or the blue handkerchief that one of them wore when she was kidnapped.
The Federal Bureau of Investigation of the United States (FBI for its acronym in English) on Wednesday released the portraits that a serial killer made of their victims in the hope that they can help their identification.
Samuel Little, who today is 78 years old and has been in prison since 2012, confessed to killing 90 people between 1970 and 2005.
The researchers, who asked the population for help in recognizing victims from these traits, say that most of Little's goals were "marginalized and vulnerable women," some of whose bodies were left unidentified and their deaths uninvestigated.
After hearing his confession, which he made last year while serving three life sentences for two murders, authorities believe that Little could be one of the worst serial killers in the history of the United States.
Little, a competitive ex-boxer, reduced his victims with blows before strangulating them, which means that there were not always "obvious signs" that the person had been killed.
Now, the authorities hope that their drawings can help to finally discover who their victims were so families could be informed.
"Without stabs or gunshot wounds, many of these deaths were not classified as homicides, but were attributed to drug overdoses, accidents or natural causes," the FBI said in an initial report last November.
"One of the most prolific serial killers in US history"
Although Little has already been convicted of three murders, the FBI believes he is responsible for many more.
Little was captured in 2012, when he was arrested for a drug-related offense in a homeless shelter in Kentucky and extradited to California.
While in police custody in Los Angeles, the agents performed DNA tests.
The results linked him to three unsolved murders of 1987 and 1989, all in Los Angeles County.
The three victims for whose murders he was convicted were beaten and strangled, before their bodies were thrown into alleyways or containers.
Before being convicted of murder, Little had already accumulated an extensive criminal record consisting of crimes ranging from armed robberies to rapes in different states.
Little's case was transferred to the FBI's Violent Crime Capture Program (ViCAP), which looks at people who commit serial violent and sexual crimes.
Later, they share their findings with the local police in different areas, in order to compare them with any pending crime.
ViCAP, in charge of conducting the complete background check on Little, found that the three murders in Los Angeles were very similar to dozens of unresolved deaths dating back to the 1970s.
Crime analyst Christina Palazzolo wrote on the FBI website that "they found a case in Odessa, Texas, which was very similar to him (his way of acting), and we could verify that he was in the area at about the same time" .
In the spring of last year, researchers interviewed Little in hopes of getting more information. Knowing that he wanted to be transferred from prison, they reached an agreement: he could be transferred if he spoke.
During the interview, Palazzolo says that Little "toured the city and the state and told us how many people he killed in each place."
Once it was over, he had confessed 90 murders. The FBI says that until now it has been able to verify 34.
Many of Little's victims were sex workers, people with substance abuse problems, and transgender women whose deaths have not been investigated or were classified as accidental at the time.
His memory of most murders was accurate, as he could give details about where they happened and what vehicle he was driving.
But he could not remember specific dates, which, according to researchers, has made it difficult to identify the victims.