Aggravated robbery charges against AFL player Trent Dumont and a co-accused have been dropped in the South Australian District Court.

The 21-year-old North Melbourne player had been on trial, along with co-accused Joshua David Lomas, after pleading not guilty to one count each of aggravated robbery.

Taxi driver Malusi Hamilton Ketse alleged Dumont and Lomas pinned him to the ground and stole $70 from him after he drove them to Banksia Park in Adelaide's north-east in the early hours of October 12, 2014.

But today, mid-trial, Prosecutor Edward Stratton Smith told the court that they were no longer proceeding with the case.

The decision comes after evidence from the taxi driver, which the court heard contradicted CCTV footage taken from inside the taxi.

The CCTV footage, played to the jury on Tuesday, did not contain sound.

Dumont's lawyer, Tony Burns, told the court Mr Ketse appeared to be speaking with the men and smiling during the taxi ride and Dumont appeared to be singing.

In his evidence, Mr Ketse described the men's behaviour in the taxi as "unruly".

"They were touching me, taking the seatbelt out ... that's not allowed," he said.

At one point during his cross-examination, Mr Ketse refused to answer further questions from the defence and proceedings were adjourned for 20 minutes.

Taxi driver Malusi Ketse was cross-examined yesterday in the Adelaide District Court. ( ABC News: Rebecca Opie )

Defence says decision to prosecute was 'scandalous'

Judge Paul Muscat explained to the jury that the prosecution had entered a "nolle prosequi", which meant the case was no longer going to proceed.

Dumont and Lomas smiled and hugged as they were discharged from the dock.

Defence counsel said it was "scandalous" that the matter had got this far and that they had numerous conversations with the Director of Public Prosecutions about the inconsistencies in the taxi driver's evidence.

"The prosecution knew two years ago ... there was always a gap in the evidence," Dumont's lawyer Tony Burns said.

"It's scandalous really that it got this far, it's cost the state and the parties a lot of money."

Judge Paul Muscat said he was not surprised the prosecution had reached that decision but also criticised how long it had taken.

"It's the right decision to make, don't get me wrong, but as Mr Burns rightly points out it's come about two years too late," he said.

Judge Muscat said he was not criticising the prosecutor who was tasked with handling the case.

"It's those who are charged with the responsibility of ensuring there is a reasonable possibility of conviction," he said.

"It shouldn't get to the stage where prosecution forms that view after its principal witness had completed giving evidence."

North Melbourne Football Club general manager Cameron Joyce said the club was happy with the outcome.

"This obviously gives Trent the chance to put everything behind him and focus on his football and the great opportunity he will have at the North Melbourne Football Club this year," he said.