Law enforcement agencies, and more importantly politicians, have been fearing the downloadable gun. Anyone could download plans from the internet, and use a cheap 3D printer to print a firearm. Additive manufacturing, to use its formal name, would democratise the manufacture of smallarms.
Those fears are turning into reality.
The 3D design files for guns are readily available. But the threat isn't from the cheap 3D printers, though, because they can only produce low-quality weapons, usually in plastic. It's from the more accurate computer-controlled milling machines, the prices of which have plummeted in recent years. They produce high-quality parts in metal.
And it's not individual criminals we should worry about, it's the organised gangs.
These observations emerged during a discussion of the potential threat from 3D-printed guns at the 5th International Conference on Cybercrime and Computer Forensics on Australia's Gold Coast on Tuesday.
A conference delegate identifying himself as being from South Australia Police said easy access to the digital design files for guns is the issue for them, not the availability of the technology used to manufacture the guns themselves.
"We've seen more manufacturing through acquired stuff off the internet in metal than in plastic. And the relative affordability now of lathes, anyone can really do that," he said.
"Silencers are made abundantly in metal from digitally downloaded plans."
Another delegate, identifying herself as from the Victoria Police, said her understanding of the current fear wasn't that "bikies and drug traffickers and the like" would buy their own cheap 3D printers and use them themselves.
"What they're going to do is stand over people who have a mid-sized commercial operation that utilises additive manufacturing. If they go in there with their own guns, their real guns, and say 'here's our 3D gun file that we've downloaded, the design file, do it or else'," she said.
Her understanding, from her conversations with e-crime investigators, was that the availability of gun design files wasn't limited to the so-called darknet.
"It is everywhere. It's just a simple Google search, because it's not criminalised [in Victoria] at the moment."
The conference session was to present research by Dr Angela Daly, a specialist in the regulation of new technologies and author of the 2016 book Socio-Legal Aspects of the 3D Printing Revolution, and her colleague Dr Monique Mann, a criminologist specialising in transnational policing, both from the Queensland University of Technology.
Their research had led them to conclude that so far the actual prevalence of 3D-printed weapons had been low, but that this was changing rapidly, particularly in Australia.
"As far as we know, there are no cases with a 3D-printed gun being used to commit any crimes in the UK, or internationally either," Daly told the conference.
"That having been said, 3D-printed gun parts have begun to turn up on a few occasions, and I really want to stress a few occasions, because I don't think we are seeing widespread 3D printing, and we're certainly not seeing widespread 3D-printed guns. However, they are beginning to turn up," she said.
"It seemed to me that there were various cases that were emerging here [in Australia] in a way that they hadn't been emerging in the UK, and really hadn't been emerging in the US as such."
The first Australian case documented by Daly and Mann was in 2015. Gold Coast resident Kyle Wirth was convicted of unlawful manufacturing of firearms, pleaded guilty, and received a six-months suspended sentence.
In 2016, an "almost factory quality" submachine gun was found at a "large scale weapons production facility" on the Gold Coast, during a raid conducted jointly by the Queensland Police Service and the Australian Border Force as part of Operation Oscar Quantum.
And in February 2017, a 27-year-old man became the first person charged under new NSW legislation specifically criminalising the possession of a "digital blueprint for manufacture of firearms" -- the only Australian state to introduce such laws -- in relation to one of four imitation pistols found on the premises.
"In these cases these properties were raided for other purposes, particularly drugs," Daly said. "[Police] happened to find 3D-printed parts, but the detection really came because these people were suspected of other kinds of crimes."
According to Daly, that raises the question of whether people are printing guns without being detected.
The only person to have been imprisoned for creating 3D-printed weapons is Yoshitomo Imura. In May 2014, Imura was arrested by Japanese authorities after he created a weapon he called "ZigZag" and posted a video to YouTube showcasing its construction and capabilities. In October 2014, he was sentenced to 24 months imprisonment.
The year before, British police seized what they claimed were parts for the "first 3D-printed gun" in the UK. After the police released images online, however, netizens identified them as "3D printer parts rather than gun parts".
The legislative question of whether the downloading of plans and the manufacture of guns requires new laws is still open.
"In Australia [as well as the UK and other developed countries], 3D-printed guns, in some respects, don't represent big problems conceptually in these jurisdictions, because guns are illegal anyway, or are strictly licensed," Daly said.
"However the US is a notable exception in this area, with the Second Amendment to the Constitution providing some form of right at least to keep and bear arms, based on the particular historical circumstances in which the US Constitution came about some centuries ago."
Indeed, the very first downloadable gun, Cody Wilson's Liberator 3D-printable single shot handgun from 2013, was, according to Daly, "a conceptual and political project, to realise some libertarian ideals around the Second Amendment".
In October 2014 an Australian Senate inquiry into firearms law and gun-related violence heard evidence relating to 3D-printed guns. Although the inquiry's report didn't recommend any new legislation at that time, it did recommend that "Australian governments investigate the requirement" for laws in this area, and "continue to monitor the risks posed by 3D manufacturing in relation to the manufacture of firearms and consider further regulatory measures if the need arises".
Despite the reports of 3D-printed weapons being found by police, Daly said the future risk is unclear.
"Our problem at the moment is that the knowledge we have around this is highly anecdotal," Daly said.
"Will this result in the decentralised manufacturing of guns in a widespread fashion, for people who might not have a lot of technical expertise, and who don't necessarily have loads of money to buy a sophisticated 3D printer at the moment? That's very much a question, because it's not even clear what the trajectory of 3D printing itself will be," she said.
"There are also questions which go beyond 3D printing about the policing of the darknet and how law enforcement can effectively control files for undesirable objects, or undesirable images on the darknet, issues of transnational policing as well.
While Daly agreed with police that criminals using hubs where more expensive equipment was available would be a "more likely model" than printing at home, that seemed the only thing that was clear.
"We're leaving with more questions than answers, which is a classic academic thing to do, and particularly when we think there is more scope for research."
Daly did seem sceptical that 3D-printed weapons would be a widespread risk, at least in the short term.
"It's important to note that it's not a particularly expedient process of making a gun," she said. It's laborious, time consuming, and in the case of "cheap and nasty" 3D printers, likely to result in badly-made parts. The safety implications are obvious.
"The NSW police, when they invested in their own 3D printer and printed a gun themselves, they found the gun more dangerous to the person firing it," Daly said.
"If you're looking for weapons, it's probably easier and cheaper to acquire them in other ways than 3D printing them. So I'm told, anyway."