It will be watched closely by detectives as people they have identified as worthy of suspicion are expected to take the stand.

Under the powers granted to the coroner, these persons of interest may be forced to explain their movements and knowledge of William's disappearance in September 2014 before the court.

All of the evidence collected by Strike Force Rosann, led by then head investigator Detective Chief Inspector Gary Jubelin, is being presented before the NSW Coroner's Court's Deputy State Coroner Harriet Grahame.

The first part of the inquest began in March this year and heard evidence from William's biological and fosters families and emergency services personnel who were on the ground the day William disappeared from his grandmother's front yard in Benaroon Drive, Kendall.

Read more: First round of evidence in William Tyrrell inquest presented to the Coroner

At this round of hearings, former Detective Chief Inspector Jubelin will not be present in an operational capacity after resigning from the NSW Police Force in May amid allegations he had allegedly used recording devices in the Tyrrell case without a warrant.

Mr Jubelin was taken off the Tyrrell case in March while he was investigated over the allegations of misconduct. He was formally charged in June and pleaded not guilty at a court hearing in Sydney on July 30 to four charges of using a recording device to record a private conversation.

The inquest is destined to conclude William was likely abducted from the front yard of his grandmother's home in 2014.

Deputy State Coroner Harriet Grahame must see sufficient evidence the three-year-old did not succumb to the rugged bushland around his grandmother's home on Benaroon Dr.

At a directions hearing for the inquest in December 2018, counsel assisting the coroner Gerard Craddock SC said it wasn't possible - yet - to conclude William was dead.

Thousands of pieces of evidence and hundreds of interviews with witnesses and persons of interest have built the case that William was taken by someone who now holds a very closely guarded secret.

A $1 million reward for information leading to return or recovery of William still stands. It is one of the biggest rewards on offer in NSW.

Anyone with information should call Crime Stoppers on 1800 333-000.