A "science nerd" who wanted to collect all the elements of the periodic table could face jail time after ordering radioactive material over the internet.
But Emmanuel Lidden, 24, will have to wait to learn his sentence after breaching nuclear non-proliferation laws by shipping samples of plutonium to his parents' suburban Sydney unit.
The incident sparked a major hazmat incident, with Australian Border Force (ABF) officials, firefighters, police and paramedics all attending the scene in August 2023.
Far from any intent to build something nefarious like a nuclear weapon with the material, Lidden's lawyer John Sutton described his client as an "innocent collector" and "science nerd" who had been left flipping burgers after being sacked from his job following the incident.
"He did not import or possess these items with any sinister intent ... these were offences committed out of pure naivety," Mr Sutton told Sydney's Downing Centre District Court on Friday.
"It was a manifestation of self-soothing retreating into collection, it could have been anything but in this case he latched onto the collection of the periodic table."
Lidden had also been a keen collector of stamps, bank notes and coins.
But prosecutors said describing the young man as a simple collector and science nerd were a mischaracterisation.
This sort of incident where "collectors" sought illegal material created a market that might not have otherwise existed, the court was told.
Mr Sutton argued border force officials had engaged in duplicitous and unfair conduct by returning some of the material to Lidden after initially seizing it.
"(Lidden) knew this was a radioactive substance but he was allowed to possess it, and perhaps he thought it was because it was a minimal quantity," Mr Sutton said.
"There was no Sherlock Holmes detection here by the ABF, the packages had (Lidden's) address and his name ... investigators were aware he had obtained this material and it was in a very small quantity."
Lidden ordered the items from a US-based science website and they were delivered to his parents' home.
The seizure of the items in the hazmat incident was described as a "circus" by Mr Sutton.
"The level of the response was a massive overreaction given what the investigative authority already knew," he added.
"Rather than give (Lidden) an opportunity to return the items, the kitchen sink was thrown at him, along with the utensils inside."
Formerly a trainee train driver, Lidden lost his job with Sydney Trains after disclosing to his employer that he was being investigated.
He now works at a fast-food restaurant flipping burgers.
"Against my legal advice, he disclosed to his employer that he had been investigated by the ABF," Mr Sutton said.
"They terminated him for lack of transparency and honesty, but how can that be?
"He hadn’t even been charged and the reward for his honesty was termination."
Lidden pleaded guilty to offences under Australia's nuclear non-proliferation act that carry a possible 10-year jail sentence.
He is due to receive his sentence from Judge Leonie Flannery on April 11.
