"People who did not agree with him would think he was obsessive but people who had trust in him would say he was dedicated," said Booth.
The subsequent Royal Commission of inquiry hailed Dr Sprott as "the man in our view more than any other ... responsible for the essential release of Mr Thomas".
For his efforts, he was awarded $50,000, which Dr Sprott said was "perhaps a third of what it cost me".
But Booth said his friend was not motivated by money.
Educated at the University of Auckland where he gained a PhD in electrochemistry, Dr Sprott ran his large firm of consulting chemists from 1952 to 1983, when he sold to retire.
From his work, his inventions included the "slikka pad" for chillybins and he led discovery of Chatham Islands peat deposits, which had potential for fuel oil, and helped set up pulp mills using exotic forests in Northland and the Central Plateau.
Once, he set out on a "one-man campaign to reduce the road toll".
He caused an uproar by saying "thugby" had a lot to answer for in terms of the carnage on roads.
He said New Zealand males were most aggressive, taking to the roads with the same aggression as they showed on the rugby fields.
A long-held Sprott contention, after decades of analysing blood-alcohol samples, was that alcohol was wrongly attacked as a major cause of the road toll.
As leader of the Peace Through Security group, he led a petition for a referendum on the Labour Government's anti-nuclear policy.
He said nuclear weapons had kept the peace by making war unthinkable and inserted an ad in a daily newspaper saying he and his wife, Marion, "welcomed the gallant crew of USS Truxton" to New Zealand.
In 1986, he and Marion and two of their three children moved to Canada.
From his new home in Vancouver, Dr Sprott claimed his research into Sudden Infant Death Syndrome, or cot-death, showed Sids was caused by gaseous poisoning from the mattress where the baby slept. The gas was formed by the action of an otherwise harmless fungus on certain chemicals within the mattress, he contended.
He also believed that toxic gases came from use of synthetic detergents to clean nappies and dummies and he claimed toxic gases came from sheepskin bedding too.
In 1995 he was made an OBE for services to forensic science and the community. A year after returning to New Zealand, in 1994, his book The Cot Death Cover Up? was published here and a version was released in Britain in 1996.
By August that year, the Herald reported that parents were snapping up polythene mattress covers on the advice of Dr Sprott, despite opposition from the Cot Death Association and medical researchers.
He retaliated by taking out a newspaper advertisement immediately before the annual Red Nose Day fundraiser questioning the work of the Cot Death Association.
In February 2000, organisers of the international conference on Sids at Auckland University gave Dr Sprott a 20-minute slot to justify his convictions. His audience was unsatisfied, saying his views remained open to rigorous scientific debate.
Professor Barry Taylor, of the paediatrics department at Otago University, said Sids researchers did not wish to comment on Dr Sprott's passing, but they viewed his legacy with regret, noting the large amounts of time and money that were spent investigating his theory.
