The murder of a grandmother who was battered and strangled in her own home more than 20 years ago is to be reinvestigated by police.

The family of Norah Smith, who was found dead in Falkirk on New Year's Day 1993, have been told officers will be looking once again at the case.

The man accused of murdering the 64-year-old, who was also known as Norah Benzie, walked free from court after the case against him was found not proven at the High Court in Glasgow.

Andrew Kemp, who is now serving life for murdering a former girlfriend in England, had been accused of repeatedly striking the pensioner with a blunt instrument and strangling her before setting fire to papers and furniture in her home to conceal evidence.

Prosecutors can now raise a case against an accused twice, following reform of centuries-old double jeopardy laws.

The Crown Office could not confirm whether Mr Kemp would be interviewed as part of the fresh investigation into Ms Smith's murder.

In 1992, pathologists said Mrs Smith had died from strangulation with a ligature and there had also been attempts to strangle her manually, with hammer blows to her body likely to have been inflicted after she died.

Kemp's counsel, Gordon Jackson, QC, lodged a special defence blaming another man for the murder.

After the not-proven verdict, Kemp, now 49, moved from Scotland to Nottingham. He was last year found guilty of the 2011 murder of his former girlfriend Leighann Wightman.

Mrs Smith's relatives travelled to court to see him convicted of the killing.

He had a history of violence against the woman and had been banned from seeing her.

On sentencing, the judge said Kemp posed a very serious risk to women he was involved with, particularly after drinking alcohol. Police described him as aggressive, volatile and extremely dangerous.

Solicitor General Lesley Thomson, QC, is leading the Crown Office review of unresolved murders, and prosecutors are to work closely with Mrs Smith's relatives to keep them up-to-date with developments.

Earlier this year, Ms Thomson said the memory of brutal scenes she had witnessed over her career made her determined to tackle historic unsolved cases.

The cold case unit was set up in June last year to take a fresh look at unsolved murders and other serious crimes.

Other cases to be re-investigated include the so-called World's End murders of Christine Eadie and Helen Scott, both 17, who were killed in 1977; and the murder of Indian waiter Surjit Singh Chhokar in 1993.

A retrial of an original accused under the Double Jeopardy (Scotland) Act can only proceed if a number of strict requirements are met, with the emergence of compelling new evidence amongst the legal tests. If an original trial was tainted, for example, through intimidation of witnesses or jury members, a second trial can go ahead.