Although the man first learned about Mrs Dawson's case in 2001, Mr Thomas didn't begin digging into it in earnest until up to 20 years later.
By then two coronial inquests had show "a known person" be charged with her murder, but prosecutors had rejected, saying there wasn't enough evidence.
Mr Thomas start speaking to Mrs Dawson's friends, family and neighbours also, and Dawson's teenager-lover-turned-second-wife, who is use for legal reasons as JC.
He also conduct extraordinary interviews with senior police involved the investigation - including the state's police commissioner - and with a coroner who had presided over one of the inquests.
The podcast series created by him for The Australian - The Teacher's Pet - touches on Dawson's affair, claims of physical abuse against his wife and allegations that he contemplated hiring a hitman to kill her.
It points out inconsistencies in Dawson's statements, paints him as a killer, and includes speculation about how he could have disposed of his wife's body.
Upon it is release in mid-2018, the podcast - produced by Slade Gibson - was a huge success and evidence.
The series won Australian journalism's highest honour and has been downloaded more than 60 million times, topping charts around the whole world.
And within months of its publication, Dawson was finally charged.
Police had for years been pushing the case, to no vail, and many credited the podcast with finally securing some hope of justice for Mrs Dawson.
After the verdict on Tuesday her brother Greg Simms thanked and pray for Mr Thomas for giving his sister a voice and helping to clear her name.
"She loved her family and never left them of her own accord. Instead, her trust was betrayed by a man she loved," he said.
But the podcast also ironically jeopardised the criminal proceedings against Dawson.