William Tyrrell's mother Karlie Tyrrell has a violent past with convictions for serious assaults and destruction of property, news.com.au can reveal.
Karlie Tyrrell, who gave a paid TV interview last Sunday saying she was the victim of domestic violence, is herself the perpetrator in three serious assaults.
Two of the assaults she has been found guilty of were against female police officers.
Now aged 29, Tyrrell's record for violence goes back to 2006, when she was 18 years old, documents obtained by news.com.au reveal.
During one assault in 2010, she punched a police officer in the face while celebrating her 22nd birthday.
William was removed from his mother's care two years later and then in September, 2014 he disappeared while playing at his foster grandmother's home at Kendall, on the NSW mid North Coast.
His abduction sparked Australia's greatest manhunt and is an ongoing investigation by the NSW Homicide Squad's Strike Force Rosann.
Tyrrell's next serious conviction, for assault occasioning actual bodily harm, common assault and destroy or damage property, occurred in early 2014, six months before three-year-old William disappeared.
William's grandmother, Natalie Collins, told news.com.au that Tyrrell assaulted the boy's biological father, Brendan Collins smashed up the Granville townhouse in which the couple was living.
Tyrrell was sentenced in Parramatta Local Court in August, 2014 over the three charges and placed under community supervision by the NSW Probation and Parole Authority.
Legal documents reveal Tyrrell is listed as having several aliases known to police.
Tyrrell will be sentenced next week for assaulting a police officer and using offensive language after she twice spat on an officer at Top Ryde shopping centre last December.
Tyrrell was with her two sons, who are the full biological brothers of William Tyrrell, at 9.30pm, when she four times called a two-woman police patrol "c**ts".
She said "f**k off you ranga c**t" before recoiling her head back and spitting twice on the female constable's eyebrow and cheek.
Tyrrell's March 19 hearing will be the second time she has been sentenced for assaulting a police officer in the execution of duty, news.com.au can reveal.
On the previous occasion, at Ryde Local Court in 2010, a magistrate rewarded Tyrrell with a 12-month good behaviour bond.
In 2009, she was twice convicted for shoplifting items valued less than A$2000 (NZ$2143) in the Ryde area and fined a total of A$400 (NZ$430).
In 2010, Tyrrell had gone to the Ryde area to celebrate her 22nd birthday with family members at her father's house. One relative was at the time subject to a court-ordered curfew.
Police were called to the house after neighbours reported noise in the street and they found Tyrrell in the road.
During a heated exchanged which ensued with a female police officer, she punched the officer in the face.
Tyrrell was convicted and sentenced in Ryde Local Court in August 2010 on charges of assaulting an officer and resisting an officer in the execution of duty, fined a total of A$500 (NZ$535)and placed on a 12-month bond.
William was removed from the care of Tyrrell and Collins in early 2012 when he was eight months old and placed with a foster family.
There is no suggestion that either William's biological family or his foster family has anything to do with his disappearance.
Child protection laws guarding the pair's identity and the fact William was fostered out were lifted by a NSW Supreme Court order late last year.
Collins is due for release after serving a two months sentence for minor theft and drug charges.