Shepherd, 36, left his cell in Category B HMP Dovegate, Staffordshire, on Tuesday, The Independent understands, after serving half of his 10-year sentence over the death of 24-year-old Charlotte Brown in December 2015.
The 36-year-old had been found guilty of manslaughter in his absence in the summer of 2018, but he subsequently went on the run to avoid justice, so he was not jailed in the UK until April 2019.
After meeting Ms Brown on the website OkCupid, London’s Old Bailey heard that Shepherd, a former IT consultant who earned £150,000 a year, had been trying to impress his date with champagne and a late-night high-speed jaunt in his boat past the Houses of Parliament.
His trial was told that he was responsible for the speedboat, which had a series of serious defects, including its steering.
Shepherd had handed the controls to Ms Brown just before the craft capsized near Wandsworth Bridge in central London after hitting a log, throwing both of them into the cold water, the court was told.
The defendant was plucked from the Thames alive, but Ms Brown, from Clacton-on-Sea, Essex, died after she was pulled from the river unconscious and unresponsive, the jury was told.
Shepherd, originally from Exeter, appeared at the Old Bailey in November 2017 when he pleaded not guilty to manslaughter by gross negligence and was granted bail.
He was found guilty in his absence in July 2018 after he skipped bail and travelled to Georgia in March of that year, jurors heard.
The defendant finally surrendered to Georgian police officers in January 2019 and was extradited back to the UK from the country.
Shepherd had originally been sentenced to six years imprisonment. He was given an extra six months for breaching bail and absconding when he was finally jailed in April 2019, but this second sentence was later quashed due to a technicality.
Shepherd also served a consecutive four-year sentence, which he was given at Exeter Crown Court in 2019 after admitting to wounding a barman during an attack in March 2018. The court heard that he struck David Beech with a vodka bottle after being asked to leave The White Hart Hotel in Newton Abbot, Devon.
Appeal judges then decided in July 2020 that the 78 days Shepherd spent in custody awaiting extradition from Georgia should count as part of the four-year sentence.
This decision brought Shepherd’s total sentence to just under 10 years. The Independent understands he was released on Tuesday after serving half of this sentence.
Ahead of Shepherd’s release, Ms Brown’s father Graham Brown begged him to reveal the truth about what happened on the tragic night of her death.
Speaking to ITV’s Good Morning Britain earlier this month, he said: “Nothing will replace losing our Charlotte.
“We still don’t know what happened that night. Because Jack Shepherd wasn’t present at his trial, so we never got to hear his version of events. It was never challenged or cross-examined.
“He subsequently fled to Georgia and on his return he let out snippets like my daughter was driving the boat which we totally disbelieve because the boat was so unworthy.”
He also paid tribute to his “wonderful” daughter who was “so full of life and so full of fun”.
He added: “She had just got a promotion and was looking forward to a successful career in the beauty industry. She was looking forward to taking her driving test, all those normal things.”