A drug case against a Perth man has been thrown out after the District Court was told by his barrister Lloyd Rayney that police destroyed a key piece of evidence and made contradictory claims.

Brendon Wyatt, 26, was represented by Mr Rayney in his first major case since the Legal Practice Board was ordered last month to re-instate his practising certificate.

Mr Wyatt had been on trial for the past four days accused of possessing $14,000 worth of methylamphetamine, which was found in a vacuum-sealed bag in a city hotel room in July 2014.

During the trial, it was revealed that a vacuum-sealing machine seized during the police investigation was destroyed without a court order and without the knowledge of defence lawyers.

In a submission to Judge Richard Keen, Mr Rayney said as well as the destruction of the machine, police had only obtained "selected" security footage from the hotel and not seized other "important" footage.

Mr Rayney said there were inconsistencies in the evidence of police, including one detective saying there was a video recording of the search of the room while another testified he believed the recording had never taken place.

It was Llloyd Rayney's first major case since regaining his right to practise law. ( ABC News: Marcus Alborn )

Mr Rayney also said police notes, claimed previously not to have existed, were subsequently found during the course of the trial.

Judge Keen ruled that on the evidence put before the court there was not enough to link Mr Wyatt to the drugs found in the room.

A woman, with whom Mr Wyatt spent the night at the hotel and who in an "agitated state" had tried to return to the room the next day, had already pleaded guilty to attempting to possess the drugs.

She received a suspended sentence but was not called to give evidence at Mr Wyatt's trial.

Significant errors by police: solicitor

Speaking after the ruling, Mr Wyatt said he was "relieved and happy" the case was over.

His solicitor Frank Mestichelli said there had been significant "protocol errors" by police.

"I think the detectives involved must stick to strict protocols in search and seizure and what has to be done for the proper conduct of the matter," Mr Mestichelli said.

"I think it is important in instances such as this that justice is seen to be done, and in this instance it has been.

"The consequences could have been severe for a young man that could face potentially 25 years in jail for an offence he did not commit."

Despite the errors, Mr Mestichelli said his client did not intend to make any official complaint against police and now hoped he could get on with his life.

State prosecutors made no submissions to the judge, only saying "based on newly disclosed evidence" and a reassessment of the case, they accepted there was "no reasonable prospect of a conviction".

WA Police said in a statement the vacuum-sealing machine "was destroyed due to an administrative error."

They said all searches conducted by police had been video recorded, and relevant CCTV footage relating to Mr Wyatt's movements had been seized.