THE sister of missing Sandy Davidson, the Irvine toddler who disappeared almost 40 years ago, has called on the police to discover if evil serial killer Angus Sinclair was to blame.

The Irvine Times can exclusively reveal this week that Sandy’s distraught family have called on police to make Sinclair, who was convicted for the World’s End murders last week, to take a lie detector test after a national newspaper revealed that secret documents in 2007 revealed Sinclair thought he would be questioned on the disappearance.

Three-year-old Sandy vanished from his grandmother’s home in Bourtreehill in April 1976 sparking an extensive search and countless appeals.

But Sandy has never been found leaving his mother Margaret and sister Donna without closure.

However, Sinclair, jailed for 37 years last Friday for the murders of Helen Scott and Christine Eadie in October 1977, was interviewed by police about Sandy’s disappearance.

Sandy’s family believe that there is a possibility that Sinclair could have been responsible.

Sinclair, who was jailed for life in 1982 for sex attacks on 11 girls, has also been linked with other killings and disappearances including that of 22-year-old Patricia Black who went missing from Irvine in October 1976.

Speaking to the Irvine Times this week, Sandy’s sister Donna urged the police to make Sinclair take a lie detector test.

She said: “They should definitely bring him in for questioning.

“It took them 37 years just to convict him for the World’s End murders so they should at least look into any links with Sandy but I’m not sure the police will go ahead and do it.

“I think he should be placed under a lie detector test but I don’t think he would agree to it.

“He’s one of those who likes playing games with people, you can see it.

“I had previously questioned the police about bringing him in again about Sandy but they were adamant that it was just girls he was involved with but you just never know, he could have been involved with boys too.” Donna and the family were dealt a fresh blow back in September when police confirmed that they would not carry out a search in the now derelict Broomlands Primary in a bid to find Sandy.

She added: “I would like to think that the police would take it upon themselves to keep me in the loop about what they’re going to do.

“I’m the one that’s constantly phoning them about any information and any new leads.

“I’ll still be chasing them up in regards to Sinclair because it’s definitely worth investigating again.” A Police Scotland spokesperson told the Times: “Police Scotland continually review all unresolved cases for opportunities presented by new information and advances in forensic science.

“The missing person inquiry into the disappearance of Sandy remains open and we welcome any new information which will be carefully investigated.

“If anyone has any information which may be relevant we would ask them to contact police on 101.”