Lucas Browne insists he is a clean athlete ahead of Saturday's heavyweight fight against Dillian Whyte and believes lie detector tests help to prove his innocence.
The Australian can boost his hopes of a world title shot with victory over Whyte at London's O2 Arena on Saturday, but his career looked finished after two failed drugs test in 2016.
Browne (25-0, 22 KOs), 38, from Sydney, was banned for six months and stripped of the WBA heavyweight title due to a failed drugs test for clenbuterol after his 10th round KO over Ruslan Chagaev in Russia back in March 2016.
Browne argues his food or water was spiked while in Russia and he was later ruled "unlikely" to have taken that substance deliberately.
However, the former nightclub bouncer failed a drugs test for the second time in eight months after testing positive for the banned substance ostarine [also called enobosarm], which led to the cancellation of a fight against Shannon Briggs, the former two-time world titleholder from Brooklyn.
"I was out in Chechyna and three days before the fight [vs. Chagaev] I had a blood and urine sample which was completely clear," Browne told ESPN. "After the fight, it came up as very marginal traces of clenbuterol.
"Now clenbuterol is a weight stripper so the idea of a heavyweight boxer using it is ridiculous. Plus, I would need to take it a lot sooner than I was supposed to have which would have been less than three days before the fight.
"I had no reason to take a weight stripper substance -- why would I need to take something two days out from a fight? It would hinder my performance.
"They have cleared me, I've gone through a lie detector test and blood tests and it's still a win on my record.
"Unfortunately the second test was my own stupidity I believe. I was preparing for the Shannon Briggs fight. I was on a supplement and if you take it for a long period of time, it stops working.
"So I got an over-the-counter supplement but on the label it didn't give the specific ingredients.
"It looks like I'm a two-time cheat, but didn't do it. I've done hair follicle and lie detector tests to prove I'm not. It absolutely left me in limbo, but I'm a clean athlete.
"I'm back to where I was before I started. I won the world title and then I spent it," Browne added. "Now, after everything that has happened, I'm back and ready to kick start it again.
"I knew I was innocent so why should I pack it in? I'm 38 but I started boxing full-time at 33 and I still have a lot left."
Whyte (22-1, 16 KOs), 29, also tested positive and served a ban for the stimulant methylhexaneamine, which was in a sports nutritional drink he bought over the counter in 2012, but the Londoner has little sympathy or interest in Browne's argument.
"We know what he has done but I don't really care, I don't know the ins and outs of it," Whyte told ESPN. "It's very strange that you fail two drugs tests in the space of a few months. The first one could be a case of contamination or spiked but two in six months is no excuse.
"With the second one, he was still in trouble with the first one, so what was he doing? Everyone makes mistakes but I'm just cracking on with it.
"As long as he hasn't been cheating ahead of my fight and hopefully he has been tested right.
"I don't want to beat him up and then it comes out as a no contest on my record because he has been cheating and tests positive for something."
Browne has had one fight -- a second-round knockout of American journeyman Matthew Greer in June -- since his career-best win over Chagaev two years ago.
However, beating highly-ranked Whyte will give Browne's career some vital momentum and believes there are still bigger tests to come.
"I don't rate Dillian Whyte that high," Browne told ESPN. "I see him as the new Dereck Chisora, he's a gatekeeper, someone I have to beat to move on to bigger things."
"There was a lot of backwards and forwards with fights before this one was announced, I was supposed to have fought Parker.
"But there's no money it in against Parker. If I fight a world title in Australia it will be for 300 or 400,000 Australian dollars, Parker would get a million, where as he's getting £9 million or more for fighting Joshua in the UK.
"The money is overseas and it's UK at the moment. In Australia, the interest is nothing compared to the UK. Here, fans get involved more and there's more money and hype."