Rikki was allegedly spotted in the company of then 13-year-old James Watson before he was strangled near his Peterborough home on November 28 1994.
The boy’s naked body was found posed in a star shape in woods off the Welland Estate the following day, the Old Bailey has heard.
Rikki’s mother Ruth Neave, who had reported him missing, was originally accused of his murder but acquitted after a trial.
Following a cold case review in 2015, Watson’s DNA was found on Rikki’s clothes, which had been dumped in a nearby wheelie bin, jurors have heard.
School cleaner Sylvia Clary spoke to police at the time about seeing Rikki with Watson on the morning of November 28.
On Monday, the now retired 90-year-old was called to give evidence at Watson’s murder trial by video link from Nottingham.
She told jurors she still remembers the sighting outside her house on the estate between 8.30-8.45am.
She was looking out of her kitchen window when she saw Rikki in his school uniform and anorak, she said.
John Price QC, prosecuting, asked: “When you saw him, was he alone or was he with someone else?”
Ms Clary replied: “With someone else.”
Mr Price said: “Did you know that other person?”
Ms Clary responded: “Yes.”
The prosecutor went on: “Who was the person that he was with?”
The witness replied: “Jamie Watson.”
Asked how she knew him, Ms Clary said: “He lived at the back of our house and his father had put my patio in.”
She told jurors Watson, who was not in school uniform, had looked at her and waved.
Cross-examining, Jennifer Dempster QC, for Watson, said: “If I suggested to you that was not James you saw with Rikki, what would you say?”
Ms Clary replied: “No, it was.”
Watson, now 40, of no fixed address, denies murder.
The trial continues.