Antivirus software pioneer John McAfee has been found dead in a suspected suicide in his Barcelona prison cell after Spain’s high court authorised his extradition to the US to face tax evasion charges.

He was also charged with cryptocurrency fraud and money laundering crimes relating to promotion of altcoins.

The justice department accused him and Jimmy Watson, executive advisor of his cryptocurrency team, of carrying out a “a pump and dump” scheme whereby they bought publicly traded altcoins at a low price before using McAfee’s Twitter account to promote the coins using “false and misleading” statements.

They made a profit by selling the coins at a higher price, allegedly netting $2m (€1.68m) in December 2017 and the following month.

McAfee disputed the allegations, saying: “No one could have foreseen the altcoin market crash. We were paid in the same coins that crashed.”

On the alleged non-payment of $4.2m in taxes, he said in 2019 that he had not paid US income taxes for eight years for ideological reasons. He was arrested in Barcelona airport last October.

During a court hearing last month, McAfee, aged 75, said that given his age, he would spend the rest of his life in jail if he were convicted in the US, Reuters news agency reported.

“I am hoping that the Spanish court will see the injustice of this. The United States wants to use me as an example,” he said.

Prison authorities are investigating the cause of his death.