Kevin Smith, 22, was left brain damaged, blind and "disorientated in time, place and person" after being struck by a van driven by John McDougall.

McDougall, who was twice over the legal drink-drive limit, was jailed for 10 months and banned from driving for five years.

Sheriff Derek Living-ston, who sentenced McDougall, said his hands were tied because the Crown had raised the prosecution at summary level, which restricts sentencing powers.

Kevin's dad, Peter, 42, told the Evening Times: "It's pathetic. This case should have gone to the High Court.

"Kevin's not been deemed important enough, it's been put in with the petty stuff.

"The judge's hands were tied. All he could do was hand out 10 months. It's a sick joke.

"We want the procur-ator fiscal's office to explain themselves. He has destroyed someone's life."

Kevin needs round the clock care, and the trial heard that life for him and his family had "changed beyond all recognition".

The Crown Office said there was "insufficient evidence in law" to bring more serious charges.

But Peter, of Barr-head, East Renfrew-shire, said: "It leaves you asking where is the justice?

"We have asked our lawyer to write to them and ask them to explain themselves.

"Everything seems to be in favour of the criminal."

The trial heard Kevin, a previously healthy young man who enjoyed life, had been under the influence of drink when he was hit by the van.

He was catapulted over the vehicle's wind-screen and on to its roof before sliding over the rear and landing on the ground in Paisley Road, Barrhead.

Paisley Sheriff Court heard Kevin suffered multiple fractures and severe brain damage. He later went blind, and suffered a major seizure and meningitis.

Earlier this year, a consultant said that Kevin had "lost all of his independence and his situation seemed unlikely to change".

Peter was almost too emotional to talk about the effect of the incident last September.

He said: "We are just destroyed. We are just angry all the time. The first thought you have is Kevin and how his recovery is going, but at the back of your mind you hope for justice.

"The sentence was just a slap in the face, just sick."

McDougall, 32, formerly of Craighead Way, Barrhead and now of Cross Street, Paisley, earlier admitted driving carelessly and while twice over the legal drink-drive limit, failing to keep a proper look-out, striking Mr Smith to his severe injury and danger of life, and failing to stop.

John McGuire, defending, admitted there was little he could say in mitigation.

In response to Peter's comments, a Crown Office spokesman, said: "These charges fully reflected the evidence in the case, in particular the manner of driving.

"There was insufficient evidence in law to libel more serious charges and as a result the case was prosecuted on summary complaint which is the only competent forum for such charges.

"There is no separate criminal offence for causing serious injury whilst driving under the influence of alcohol or whilst driving carelessly."

Road safety campaign group Brake called for tougher sentencing for drink drivers.

Spokesman Richard Coteau said: "As a charity that supports road crash victims, we know the appalling suffering that results from drivers who take the selfish risk of drink driving. We believe tougher sentences should be meted out in cases like this, in line with the pain and devastation inflicted.

"Tougher penalties for all drivers who take risks at the wheel – but particularly where this has led to a casualty – would act as a better deterrent."

ewan.fergus@ eveningtimes.co.uk