An Adelaide man found in possession of an "improvised hand grenade" he said he bought during an online classifieds transaction has been sentenced to up to a year in jail.
Konrad Jan Kosznik, 36, previously pleaded guilty to one count of possessing an explosive device.
The District Court in Adelaide heard he bought the "particularly powerful" firecracker, which contained almost 150 nails and rocks, at the same time as purchasing two jumpers on Gumtree.
Kosznik told the court he spent $50 on the item.
He said he was promised the device would make a "big boom" and that he bought it to relive his childhood in Poland where fireworks are legal.
It was found in his backpack by police about six months later in June 2019, after he was stopped for not wearing a helmet while riding a bike.
"I completely forgot I had it," Kosznik told the court last week.
He said his decision to purchase the device had brought shame upon his family and was "just a silly, stupid mistake".
"I'm not a terrorist. I don't make bombs. I don't have the mind to make bombs anyway," he said.
"I don't hurt anybody in my life, I've never been in any punch-ups … I don't have any enemies."
Judge Michael Boylan said Kosznik had given inconsistent statements and rejected his explanations about how he had acquired the device and why he was carrying it the night he was searched by police.
He said Kosznik would not be sentenced for manufacturing the device, even though some nails strapped to the firecracker — described by prosecutors as an "improvised hand grenade" — matched those in a jar in his bedroom.
Judge Boylan acknowledged Kosznik intended to detonate the device in a paddock in Two Wells.
"Even if you didn't intend to use it for any sinister purpose, if it came into the hands of others it could've caused much harm," he said.
"I'm told you are remorseful for your conduct and embarrassed by it.
"My first duty is the protection of the community."
Kosznik was sentenced to up to a year in prison, with a non-parole period of six months.
