The safety of the conviction of Phuong Ngo for the 1994 murder of the Labor MP for Cabramatta John Newman has been blown apart by sensational evidence to a judicial inquiry into Australia’s first political assassination.

Former NSW Health Minister Reba Meagher, who succeeded Newman in the Cabramatta electorate until her resignation from state parliament in September, has exploded the Crown’s case which led to Ngo’s conviction and life sentence at his third trial.

Meagher testified that former ALP general secretary John Della Bosca offered her Newman’s seat just hours before he was gunned down in the driveway of his home.

And 90 minutes after Newman’s slaying, Della Bosca called her to ask her to make a decision on accepting Newman’s (now vacated) seat.

Events on the fateful day, September 5, 1994, can now be reconstructed:

Midday: Reba Meagher, then a 26-year-old right-wing Young Labor gauleiter, received a phone call from Della Bosca inviting her to a meeting at his Sussex Street office at 4pm.

1pm: Della Bosca holds a pre-arranged lunch in Chinatown with Ngo, a Labor branch stacker and ALP councillor on Fairfield City Council. Della Bosca and Ngo were both educated by De La Salle priests.

4pm: Meagher, accompanied by her political accomplice Joe Tripodi, another Young Labor operative, meet Della Bosca at which he offered her either the Cabramatta or St Marys seat. Both seats had already pre-selected their sitting MPs — Newman in Cabramatta and Tony Aquilina in St Marys — but “Della” informed the couple that “there were problems with two members of parliament who probably would not be contesting the next election”.

Meagher told Judge Patten she had “eyes as big as saucers” when she heard the offer.

9.30 pm: Newman gunned down in front of his fiancee, Lucy Wang, as he parked his car at his home in south-western Sydney.

11pm: Della Bosca phoned Meagher at home asking her to a meeting the following morning. “I would have to make up my mind [that night] whether I was willing to be the candidate for Cabramatta and I was required to attend Sussex Street by 9am the following morning,” she testified.

The next day Meagher was gifted Cabramatta which she won, first at a by-election in October 1994, and then at the 1995, 1999, 2003 and 2007 elections without facing a pre-selection.

Her close associate, Tripodi, shafted Geoff Irwin in the neighbouring seat of Fairfield and became the MP in 1995. He too has never faced a rank-and-file pre-selection.

The Crown case against Ngo rested on his political ambition to grab the seat of Cabramatta from his Labor rival and anti-drugs campaigner Newman.

But from Meagher we now know that she was the ALP’s “pea” for the seat and that plans were afoot to unload him before the 1995 election.

Sending Ngo to jail for the rest of his life, Justice John Dunford accepted the Crown’s motive by saying that Ngo’s downfall was due to “naked political ambition”. He added: “In seeking to become the member for Cabramatta he not only deprived John Newman of his life, but destroyed any further potential which he himself may have had.”

In fact, Ngo’s ambition was to seek a spot in the NSW upper house and not use his formidable branch stacking skills — he holds the all-time ALP record of recruiting 500 new members in a couple of days — to oust Newman.

Judge Patten has no choice but to issue a summons to Della Bosca, now the Health Minister, to give evidence at the Ngo inquiry and also Tripodi, the Finance, Infrastructure, Regulatory Reform, Ports and Waterways Minister.

There was also previous evidence at Ngo’s trial that former Premier Bob Carr and Della Bosca discussed dumping Newman — Carr says he has no recollection of it. Carr should be taken from his taxing efforts on behalf of Macquarie Bank to testify as well.