For many women, a hair straightener is one of the most useful tools they own.

But for Bronwyn Joy Parker, 22, of Mount Barker in South Australia, her hair straightener became more than a secret weapon.

Ms Parker, who had a history of violence towards her former boyfriend, used her hair straightener to burn his tongue and penis.

After discovering he'd lied to her, she told him to stick out his tongue - which she burnt with the hot ceramic plates of her hair straightener, instantly causing it to blister.

"He lied to me about something and I said, 'you know, the next time you lie to me, I'm just going to straighten your tongue'," Ms Parker told SA police in December 2013.

"He lied to me, so I sizzled his tongue for, like, one second, if that."

She then issued him another warning: if he ever cheated on her, she would burn his testicles. He agreed, thinking she couldn't possibly be serious.

After she learned he was sleeping with his ex-girlfriend in December 2013, Ms Parker reminded her former boyfriend of the agreed punishment.

Surprisingly, he agreed - but only if Ms Parker applied the hair straightener to his penis, not his testicles.

"He ended up pulling down his pants, I could tell he was nervous," she told police following the incident.

"Obviously it was going to hurt. But, you know, I literally didn't think it would burn as bad as it did. I put it on for maybe one second and pulled it straight off."

She expected it would only cause an injury similar to sunburn.

"It didn't look too bad, it just looked as if you had cooked a piece of meat," she told police.

In fact, applying her ceramic hair straighter to her former boyfriend's penis caused third-degree burns.

Ms Parked faced Adelaide District Court on a charge of recklessly causing serious harm.

"The healing and scarring process may take up to two years to complete," District Court Judge Paul Muscat told Ms Parker.

"In short, his penis will be scarred for life."

After entering an 18-month good behaviour bond, Judge Muscat handed Ms Parker a nine month suspended sentence.

After examining the case, Queen's Counsel David Galbally said: "I've never seen a case like this that's involved such a vitriolic attack."

"The sort of injuries and the assault itself is so out of the ordinary, its an extraordinary set of facts," Mr Galbally told A Current Affair .

"I have never heard of a hair straightener being used in this way at all.