The disgraced ex-politician is to be freed from Dumfries Prison by the weekend, a decision that was criticised yesterday.
Walker, elected as the SNP MSP for Dunfermline at the last Holyrood poll, was exposed as a serial abuser of women by the Sunday Herald two years ago.
This newspaper revealed a string of violent assaults that spanned 30 years, three ex-wives and a former teenage step-daughter. The SNP suspended Walker and the revelations triggered a police investigation that led to him being charged with multiple counts of assault.
During his trial last year, Sheriff Kathrine Mackie heard how Walker gave his first wife Maureen Traquair a black eye days before their wedding in 1967.
His second wife, Anne Gruber, told the court that Walker had kicked and punched her, as well as knocking her to the ground.
She also alleged in court that he raped her, although this was not one of the charges.
Walker's third wife, Diana, testified that the politician repeatedly struck her over the course of their unhappy marriage.
He was also accused of smashing a saucepan over the head of his former step-daughter.
The sheriff found Walker guilty and sentenced him to 12 months, which was the maximum penalty available to the court.
She said: "There was evidence showing the accused to be controlling, domineering, demeaning and belittling towards the three complainers, his former wives.
"The evidence also showed him to be untrustworthy, disloyal and unfaithful towards others including his present wife."
Following the verdict, a spokesman for Walker released a statement claiming that one of the former wives had been "enjoying the limelight" during the case.
The spokesman later said he had felt pressured by Walker into sending the statement out in his own name.
Walker then resigned as an MSP after doggedly refusing to quit.
The Sunday Herald can reveal that he will be released from prison within days - just six months into his sentence.
He is planning to appeal against his conviction and has a court hearing scheduled for April 17.
It was also reported last year that Walker had been giving prison talks on independence to his fellow convicts. The Dumfries institution holds two types of prisoners: untried and convicted short-term prisoners; as well as sex offenders.
According to an inspectorate report, recreation facilities include pool, darts, table tennis, DVD games, dominoes and television.
Murdo Fraser, the Tory MSP for Mid Scotland and Fife, said: "This just exposes the nonsense of automatic early release. The public expects someone who is sent to jail for violent offences to serve the time they have been given. People will again be dismayed to learn that offenders can walk out halfway through their sentence."
Graeme Pearson, a former senior police officer and now Scottish Labour's Justice spokesman, said: "Many people will be disappointed Bill Walker has only served six months of a 12-month sentence. If anything, this is likely to focus people's minds that the sentence people get in court is not the time they serve in practice."
A spokesperson for the Scottish Prison Service declined to comment.