A strategically deployed tracking device helped gardaí monitor the entire production, importation, storage, and distribution network of a drugs gang.
The emitter was focused on one individual and it pinpointed vehicles, criminals, and goods involved in the operation.
In other cases it is believed that bugs planted on dissident republicans helped head off possible attacks.
These were among hundreds of incidents where spy equipment was used by gardaí on suspected criminals in the first 26 months of the controversial surveillance act.
Drugs smugglers, violent gangs, and paramilitary groups have all been spied on for months at a time by gardaí availing of their new powers.
However, the level of investment required for these investigations, in money and time, has tempered the extent to which permission is granted for surveillance sessions.
Tracking devices, because they are cheaper and less intrusive, have been the most popular spying tool available to the Garda investigators.
However, they were still used less than 200 times by gardaí in the first two years of the surveillance act.
The length of time for which these operations were authorised varied.
One in every five people tracked had devices authorised for the maximum four-month period.
However, the independent watchdog for State surveillance, Mr Justice Kevin Feeney, said in a significant minority of cases the long-term searches were scaled back before the time limit elapsed.
“In almost half the cases where the instances where the [maximum] four-month period was granted the device was in fact deactivated and retrieved within the four-month period,” he said.
In addition to trackers, bugging tools, and secret cameras were also used by gardaí.
The majority of these were set up to record subversive activity and dissident events. Normally court approval was not sought and instead, permission was received from a senior officer for less than three days.
“Due to the urgent nature of the approvals, the vast majority related to audio surveillance only and only a small number did the approvals also cover the use of a camera,” said Mr Justice Feeney.
“The main area of investigation related to subversive activities but the approvals also covered other criminal activities.”
There was a small double-digit number of cases where permission to snoop was sought from a district court. However, there were twice as many incidents where the gardaí applied to one of their senior officers for urgent authorisation.
The failure to go to the district court to obtain an order was said to be because the information about the location of the event was often not known until shortly before it happened.
In urgent circumstances, gardaí can get approval for snooping from a senior officer.
Despite their success in evidence gathering, gardaí have been slow to use the surveillance devices for a number of reasons.
Firstly, they are costly to use and require a lot of manpower to maintain extended monitoring.
Secondly, it is considered dangerous to fit the equipment without being detected by the suspected criminals.
Thirdly, while the spying is done in private, the evidence is liable to be used in open court where the investigator involved could be identified.
It is only recently that the results of criminal surveillance investigations have started to appear in court.
Not all applications to install devices have been approved.
In the first year, fewer than 10 applications were refused. In most cases this was because the request was considered premature or excessive.
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