Errors and a lack of detail in police reports mean the ACT Ombudsman cannot be sure if officers have acted within the law when they have executed covert surveillance warrants.
Ombudsman Michael Manthorpe said "inconsistencies, errors and a varying level of detail" in police reports meant his office could not always tell whether a warrant had been executed properly.
"We were not always able to determine whether ACT Policing's actions were consistent with the authority of the warrant," Mr Manthorpe said in his latest annual report.
"ACT Policing advised it has amended its guidance material and taken action to raise awareness amongst officers exercising these powers."
Mr Manthorpe said there had been one instance where ACT police "inadvertently used a surveillance device outside of a state or territory of the Commonwealth", but they took appropriate steps to mitigate the effects of that non-compliance.
He said ACT police had a lack of rules around destroying information they got using surveillance devices, and that presented a risk.
"We recommended ACT Policing establish a destructions regime that allows it to identify, on a periodic basis, whether records are required to be kept for a stated purpose," Mr Manthorpe said.
"ACT Policing advised us of action it is taking in line with our recommendation."
A "special projects" report published by ACT Policing in December said officers had been granted 35 surveillance device warrants in 2019-20.
The report said 13 of the warrants allowed police to install tracking devices. Police made four arrests based on surveillance device information in the past financial year, and one prosecution as a result.
ACT Policing was also allowed to conduct six "controlled" operations, where officers who take part are granted immunity if they commit crimes to obtain evidence.
The report said two controlled operations did not go ahead, while another ended in failure.
Police had tried to sting someone over 49 days for trafficking methamphetamine, manufacturing a drug, and making demands accompanied by threats to kill or inflict grievous bodily harm.
"All attempts to engage with [the] subject failed," the report said.
Another 84-day operation was partly successful - the outcome was listed as "controlled drugs were purchased", but police made no arrests because of the operation.
A 47-day sting ended in a person being arrested and charged with five counts of trafficking heroin.
The sixth operation also went over 84 days, and targeted someone for shooting at a person, arson, and aggravated burglary.
It appeared to have garnered little results, with the outcome listed as: "Minimal engagement was maintained between the participant and the target."
No arrests were made because of that operation.