Very bad dogs get a lot of very bad press.
But, there are reasons why a dog turns aggressive and you can probably guess what that is.
Kiwi director Erin Wilson has made a film about a couple in Sydney who have dedicated their lives to saving hundreds of damaged dogs from death row.
Jacob and Jennah Leezak rehabilitate and live with as many as 40 dogs at a time, abandoned or aggressive pets, dogs on death row.
"There's a lack of knowledge, lack of understanding where these dogs came. They have no understanding of where the dog's going," Mr Leezak says.
By overcoming their own troubled past the Leezak's have been able to help these dogs have a better life.
"To put it in an Aussie way, I was raised as rough as guts, went to a military school at the age of 12, cos my dad thought that was the best thing and sanest thing to do," Mr Leezak says.
His wife Jennah says she was born a heroin junkie.
"My mum was a junkie, she sold me to pay off a heroin debt, they found me in a dumpster when I was six months old."
Mr Wilson said he grew up with dogs and it was his mum that got him on to the Leezaks.
He emailed them and within a week he and his camera crew were on a plane to Sydney.
Watch the full interview with The Project team in the video above.