Pickering died in March after suffering a heart attack at a secure psychiatric unit.
He had been locked up for more than 45 years after killing 14-year-old Shirley Boldy in the Barnsley area of South Yorkshire in 1972.
The 80-year-old was awaiting sentencing for raping an 18-year-old woman, who is now in her 60s, a few weeks prior to Shirley's abduction.
After Pickering's death, West Yorkshire Police confirmed officers were expecting to charge him with the murder of another 14-year-old, Elsie Frost, whose body was found in Wakefield in 1965.
Pickering had been held under a hospital order made by a judge in 1972 after he admitted Shirley's manslaughter by diminished responsibility.
She was bundled into Pickering's van as she was returning to Wombwell High School.
Pickering drove her to a secluded location where he tied her up and raped her.
He tried to strangle her before stabbing her to death, a crime witnessed by walkers who were too far away to intervene.
Pickering killed Shirley just three or four weeks after he abducted and violently raped an 18-year-old woman in the Barnsley area.
In March, the victim described to a jury how Pickering had told her she was going to die. She called him a "monster".
Pickering was convicted at Leeds Crown Court of rape and false imprisonment but died before he could be sentenced.
This crime only came to light through the re-investigation of the murder of Elsie Frost.
Elsie was stabbed in the back and head as she walked through a railway tunnel in Wakefield, West Yorkshire, in October 1965.
As part of the inquiry detectives found a storage garage Pickering rented in the Owlerton area of Sheffield containing possessions including handcuffs and exercise books filled with his rantings.
One note written in 1970 said: "Sex is predominant in my mind - eclipsing all else. Maybe I will be a sex maniac proper. Rape, torture, kill."
Speaking after Pickering's death, Elsie's brother Colin, who pushed for the re-investigation of the case three years ago along with his sister, Anne Cleave, said: "It's just an incredible feeling of frustration now."
He said the family felt they had been "cheated" out of getting justice and believed Pickering could be responsible for other murders.
The case will be heard by High Court Judge Mr Justice Goss at Sheffield Crown Court on Friday morning.