A US federal agent has been sentenced to over six years in prison for soliciting $50,000 (£32,321, €44,093) worth of bitcoins during government investigations into the online black marketplace Silk Road. Carl Force, a former agent with the US Drug Enforcement Administration (DEA), apologised to his family and the US public during the sentencing on 19 October.

Force admitted to charges of extortion, money laundering and obstruction of justice, but cited mental health issues in his defence. It was revealed during the trial that Force posed as a drug dealer in order to trick the alleged Silk Road founder Ross "Dread Pirate Roberts" Ulbricht in order to garner information about the dark web site. Ulbricht paid $50,000 to Force after the DEA agent said he had information regarding a federal investigation into Ulbricht.

Force did not declare the funds to the DEA and instead secretly channelled the funds into his own personal accounts. Ulbricht was sentenced to life in prison earlier this year after being found guilty of several charges relating to Silk Road, including distributing drugs through the internet.

"The extent and the scope of Mr Force's betrayal of public trust is quite simply breathtaking," US District Judge Richard Seeborg said during the trial. "It is compounded by the fact that it appears to have been motivated by greed and thrill seeking, including the pursuit of a book and movie deal."

Another agent, Shaun Bridges, was charged alongside Force in March and pleaded guilty in September to money laundering and obstruction of justice. Force and Bridges have been barred from communicating with each other.

"I'm sorry," Force said during the sentencing. "I lost it and I don't understand a lot of it." Bridges is due to be sentenced in December.