The South Australian bomb squad described a firecracker containing almost 150 nails and rocks as an "improvised hand grenade" which was found in the possession of a man in Adelaide's northern suburbs, a court has heard.
Konrad Jan Kosznik, 36, will be sentenced in the District Court later this month after pleading guilty to one count of possessing an explosive device at Paralowie in June 2019.
The court was told that Kosznik was riding his bicycle when he was stopped by police and his backpack was searched.
Inside his backpack was a firecracker containing a cardboard tube housing 146 nails, rocks and gravel.
Prosecutors today called for Kosznik to be jailed for the offence.
"A police officer from the bomb response unit analysed the device and ultimately found that due to the rocks and the gravel, it would appear to function as shrapnel," the prosecutor said.
"It turned the device into what was effectively an improvised hand grenade.
"The police officer found the device ultimately posed a significant risk to anyone within 10 metres of the device should it explode."
He said it was a "significant device" that posed a risk to the community.
But lawyers for Kosznik told the court that he never planned to use the device for "nefarious purposes" and he bought it out of "stupidity and naivety".
They said he met a man on Gumtree and was buying clothes when he was offered the firecracker for $50 and was told if ignited, it would "make a big boom".
"In Poland, firecrackers are entirely legal. Poland is where Mr Kosznik grew up and that's what underlies his naivety to this offence," his lawyer told the court.
"When he was offered a firecracker for $50 — that he was told would make a very big bang if set off — he had no hesitation in purchasing it."
The court was told that if Kosznik did ignite the firecracker, he would have done so in a paddock.
"He had not other use or need for it, other than that," his lawyer said.
Kosznik has played A-grade soccer for the Croydon Kings, Modbury Jets and Adelaide City.
