A spate of four similar failings before Chief Magistrate Lorraine Walker recently, some of which caused prosecutions to be aborted, has prompted her to warn "something needs to be done".

An ACT police spokeswoman told Fairfax Media the recent oversights were being investigated as a matter of priority, but said they appeared to be only small in number compared to the thousands of subpoenas the force processes efficiently each year.

A Canberra man was due to face a hearing in the ACT Magistrates Court on Friday morning for three common assaults.

But it soon emerged that police had not served a subpoena on his alleged victim, who did not turn up to give evidence.

The prosecution was denied an adjournment to track her down and have her served, and was forced to push ahead with its case.

But it ran into more problems when another key witness, said to have seen some of the violence, failed to show up.

The court heard she had previously told police she would not be showing up and made disparaging remarks about the alleged victim.

Police believed they had properly subpoenaed that witness, but could not give the court proper proof that she had been served, leaving Ms Walker unable to issue a warrant for her arrest.

Ms Walker expressed her frustration and said she had been involved in four recent cases where subpoenas were not properly handed to witnesses or complainants, causing some prosecutions to collapse, and otherwise taking up large chunks of court time.

She described the failings as of "great concern to the court".

"Something needs to be done to rectify this concern," Ms Walker said.

The prosecution again decided to push ahead with its case, despite only having a single remaining police witness.

But it was given a reprieve by the court, which granted a last-minute adjournment late on Friday afternoon.

The hearing will now take place on Wednesday.

"[I attribute] this unfortunate outcome very much at the feet of, I'm not going to name individuals or organisations, but the system that has failed to ensure subpoenas were served appropriately," Ms Walker said.

The court has limited blocks of time to fit hearings into, making it crucial that witnesses be present and ready to give evidence.

A failure to do so can create significant delays in the case getting on, a problem exacerbated when the defendant is in custody.

Earlier on Friday, Ms Walker warned that: "The reality is if this matter does not proceed today, it is unlikely proceed this year.

"It is of great concern to the court that so much court time has been wasted."

Fairfax Media revealed earlier this week that a case collapsed after officers "forgot" to show up to court, and also failed to subpoena the complainant.

That meant charges against the accused, a Canberra property developer who cannot be named, were dropped.

That case has prompted an internal investigation within ACT Policing.

But the polcie spokeswoman said the errors were not reflective of ACT Policing's overall track record in dealing with subpoenas.

"ACT Policing has in place a very efficient business area that registers and serves thousands of subpoenas each year," she said.

"The full circumstances around what appears to have been a failure to serve a small number of recent subpoenas is being examined as a matter of priority."