That horrific day in 1996 when 35 Australians killed by mass killer Martin Bryant - made the Prime Minister at that time, John Howard introduce a new gun legislation that banned automatic and semi automatic firearms in Australia.

21 years since Port Arthur, how easy is it to get a gun in Australia? How many are legally registered? And what is the size of the illicit gun market? Andrew Goldsmith, Strategic Professor in Criminal Justice at Flinders University in South Australia explains.