Colin Ross ambushed 57-year-old primary school teacher Marty Layman-Mendonca in woods on the Great Glen Way, at Blackwood above Loch Ness, near Inverness, in July 2006.
He battered her at least 19 times on the head with a metal bar and a boulder, leaving her for dead in a ditch.
She was left in a coma and died several months later after being flown back to the US.
Ross admitted attempted murder and was told by judge Lord Wheatley at the High Court in Edinburgh that he would spend a minimum of 20 years in prison before being considered for parole.
He also became the first person to be made the subject of an Order of Lifelong Restriction, which would mean stringent supervision upon any release from prison.
His appeal against sentence was sent to the Scottish Criminal Cases Review Commission, who has now referred the case back to the the High Court, claiming the punishment part of 20 years was “excessive”.
Three judges will preside at a hearing on 12 February to decide on how the appeal against sentence will proceed.
Ms Layman-Mendonca was on her third visit to Scotland when she was attacked by Ross.
She had been walking the last six miles of a solo trek along the Great Glen Ways, south of Inverness, when Ross attacked her with a metal pipe.
After assaulting Ms Layman-Mendonca, Ross stole from her, tied her wrists together with shoelaces and dumped her in woods.
She was initially treated at Raigmore Hospital in Inverness, but was later flown to a medical centre near her home in Vermont in September.
Ms Layman-Mendonca was later transferred to a rehabilitation centre in Bangor, Maine, to be near her daughter, Jody Layman, where she died.
The daughter, who is awaiting further details about appeal, said her wish was that “Ross would never be released”.
Ross had been the subject of a Sexual Offence Prevention Order when he launched his attack.
Less than a month earlier, he had been freed from a three-year jail sentence for attacking a female German tourist near Cawdor Castle in 2004.
And only days earlier police had won an interim sexual offences prevention order banning him from approaching any woman without reasonable cause or excuse.
It also banned him from carrying a balaclava, ski mask or any garment that could be adapted to make a mask.
The Scottish Criminal Cases Review Commission has allowed Ross to challenge the length of his jail term.
A spokesman said: “On December 19, 2006, at Edinburgh High Court, Mr Ross was convicted of attempted murder.
“An order for Lifelong Restriction with a punishment part of 20 years was imposed upon him.
“The commission has decided to refer Mr Ross’s sentence to the High Court because it believes the punishment part is excessive.”
The commission said it was unable to make its reasons public.
At the time of the assault, Ms Layman-Mendonca was staying with Jack Fraser, of Avoch on the Black Isle, after they met through the Church of God, whose members regularly visited her when she was in Raigmore Hospital.
Mr Fraser, who now lives near Banff, said he hoped Ross would never be released from prison, adding: “What he did to her was horrible.”
Retired Church of God minister Sheila McLaughlan said: “He was so violent. He should never have been let out in the world after the first time he attacked someone.”
Ross’ solicitors and the Crown Office have declined to comment on the appeal.