A former South Australian police officer who ran a "one-stop shop" online drug trafficking syndicate probably would have ended up dead if he had not been arrested, the South Australian District Court has heard.

Thomas James Booker, 28, has pleaded guilty to more than 50 offences, including commercial drug trafficking and money laundering.

During a pre-sentence hearing, prosecutor James Watson told the court Booker was the head of the "sophisticated operation" with his offending spanning nearly two years and involving "a variety of drugs".

"He a sold a number of substances in what I would describe as a 'highly efficient manner' and effectively created a system where an individual could fulfil a number of positions in the supply chain — imports, storing substances to selling them," he said.

"The proficiency of the scheme is quite staggering.

"The offending was conducted plainly with the intent of turning significant profit and it was successful in that end."

Mr Watson told the court while Booker could not be further punished because he was a former police officer, he would have "seen the harm" drugs caused in the community.

The court heard Booker was a police officer with SA Police between 2014 and 2018.

The court heard Booker's wife took her life eight weeks after they were married in 2018, with her death the subject of a coronial inquest.

Booker's lawyer Casey Isaacs told the court his wife's death, along with the trauma he saw and experienced while a police officer led to his "demise" into drug use and trafficking.

"In the midst of his mental distress he reached out to previous colleagues … unfortunately he received no response but rather an ambulance turned up on his doorstep," he said.

"In a fairly short period of time he's lost his wife, he's lost his career and lost the support of his colleagues and friends."

Dark web activity increased during COVID

Mr Isaacs told the court Booker then got a job at the local pub, but lost it when the COVID pandemic hit.

"Effectively that's when his activity in terms of the sale of drugs and his activity as a vendor on the dark web increased," Mr Isaacs told the court.

"He found that when the COVID and particularly during quarantine stages, he was receiving a large amount of enquires and sales and his businesses — if I can refer to it as that — increased."

Mr Isaacs told the court Booker also developed a "substantial cocaine addiction" during that time, spending almost $10,000 a week on the substance.

Mr Isaacs said Booker had written a letter of apology to the court and had shown genuine contrition for his crimes, including agreeing to forfeit the large amount of money and crypto currency seized during the police investigation.

Booker has been in custody since his arrest in November 2021.

He will be sentenced at a later date.