The "surprising" assertion prompted a concerned magistrate to remark that "there is perhaps some systemic deficiency in the training".

But the Australian Federal Police professional standards division disagreed, finding in response to a complaint that its interviewing training was "sufficient and appropriate".

The Canberra Times has obtained transcripts of an ACT Magistrates Court hearing, during which defence barrister Jack Pappas grilled Senior Constable Shaun Cunningham about why he had kept questioning a driver who had made clear several times that she did not wish to answer anything more.

The officer and Detective Senior Constable Bradley Stapleton had pulled over Thuy Tran, who was charged as a result of the traffic stop with drug trafficking, drug-driving and drug possession, in Flynn.

Senior Constable Cunningham told the court he had been trained at the AFP College to continue asking questions if someone withdrew their consent to be interviewed partway through.

He justified this by saying: "If they don't want to answer questions, that's entirely their right. However, they still also have a right to hear what the allegation is, hear anything that we have to say. Whether or not they want to make comment or not, that's completely up to them."

Magistrate Peter Morrison described this testimony as "surprising".

Commenting on a number of issues arising from police conduct in the case, he directed that a transcript of the proceedings be forwarded to the ACT chief police officer.

"It seems to me ... there is perhaps some systemic deficiency in the training of police officers in the territory," Mr Morrison said.

The magistrate ultimately dismissed three of the four charges against Ms Tran, finding that key pieces of evidence against her were legally inadmissible.

She was convicted of drug-driving, but successfully appealed against that verdict when Justice Chrissa Loukas-Karlsson found in the ACT Supreme Court that roadside drug screening test and oral fluid analysis results should also be thrown out.

Ms Tran's solicitor, Tom Taylor, made a formal complaint to the Australian Federal Police on her behalf about the conduct of the officers whose "improprieties" had resulted in the exclusion of evidence.

In a letter to then-chief police officer Ray Johnson last year, Mr Taylor said it was "deeply troubling" that Senior Constable Cunningham claimed to have been trained to ignore suspects' indications that they did not wish to answer questions.

"There is a strong legal basis for the proposition that police should not persist with the interrogation of a suspect when he or she indicates they do not wish to answer further questions," he wrote.

Mr Taylor asked whether police would consider a review into the training officers received in relation to interviewing suspects.

Detective Acting Superintendent Peta Maddigan, of AFP Professional Standards, wrote back nine months later that "the training and related practices issues were explored and it was determined that existing interviewing training was sufficient and appropriate".

"[Senior Constable] Cunningham considered he unintentionally failed to 'actively listen' during the interview with Ms Tran," she wrote.

"The request to immediately stop the interview was confused by the fact Ms Tran continued answering some questions and not others.

"[Senior Constable Cunningham's] conduct was not oppressive, persistent or intimidating in nature."

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