The mother of murdered toddler Jaidyn Leskie has appealed to the man acquitted of his murder to come clean about her boy's death.

Bilynda Williams has written to Greg Domaszewicz, urging him to tell the truth.

"Please, before you die, write down (what happened) and store it somewhere," she said in the letter published by News Corp Australia's Herald Sun on Sunday.

"Please, if anything, for Jaidyn, let the truth be known to all."

Mr Domaszewicz was charged with Jaidyn's murder but acquitted by a Supreme Court jury.