By Chris Summers
On Wednesday a Canadian judge cleared two Sikhs of planting a bomb which blew up an Air India jumbo jet over the Atlantic in 1985. It claimed the lives of 329 people, 82 of them children.
More than 130 bodies were recovered from the ocean
The bombing of Air India's Flight 182 took place three years before the Lockerbie disaster but the fact it came down over the sea made it far harder for investigators.
While the debris of the Pan-Am jet was scattered across a Scottish hillside, the devastated fuselage of the Indian jumbo jet ended up 6,700 feet under the waves of the Atlantic Ocean.
When the plane disappeared from air traffic controllers' screens there were no immediate clues about what had happened.
The pilot, Captain Hanse Singh Narenda, had not reported any problem with the Boeing 747, which was en route to London's Heathrow airport from Montreal, having picked up a number of passengers and baggage from Toronto and Vancouver.
But within days, Canadian investigator Arthur La Flamme confirmed that a cockpit microphone had picked up a dull bang, a gushing noise and a human shriek in the moments before the plane vanished.
DEAD, JAILED AND ACQUITTED
Talwinder Singh Parmar - the mastermind. He was killed by police in India in 1992
Inderjit Singh Reyat - admitted assisting with the construction of the bomb, but denied knowing its intended target. Jailed for five years in 2003
Ripudaman Singh Malik - acquitted of financing the bomb plot.
Ajaib Singh Bagri - acquitted of transporting the bomb to Vancouver airport.
Examination of the 131 bodies recovered from the sea in the days after the crash showed no signs of any explosion.
But investigators soon realised the bodies belonged to passengers who had been sitting at the rear of the plane.
They were not killed by the initial explosion and some may even have survived the terrifying dive into the sea, only to be drowned in the most awful circumstances imaginable.
In the weeks following the crash, Canadian, British, Irish, French and Indian experts all volunteered their expertise in an attempt to find the wreckage, which might provide key clues.
A Scarab underwater vessel, operating from a French cable-laying ship, scoured the ocean floor.
It was a painstaking business. It took three hours to dive to the site and 36 hours for each piece to be lifted from the seabed.
Eventually, on 12 July 1985, the flight data recorder, or black box, was recovered.
Pieces of the puzzle
In October that year, salvage vessels recovered six more key pieces of fuselage.
Investigators were able to use them to piece together what happened on Flight 182.
Dr Christopher Peel, a world-renowned air safety expert from Britain's Oxford University, told the Air India trial the damage to the plane was consistent with an explosion in the cargo hold.
He said the bomb was likely to have been packed in a suitcase in cargo bin 52-left, which had been loaded in Vancouver and transferred onto Flight 182 at Toronto.
Investigators traced back all luggage on the plane and the trail led to a brown Samsonite suitcase which had apparently belonged to a Mr M Singh.
Ticketing agent Jeanne Bakermans told the trial she mistakenly checked his suitcase onto a Vancouver-Toronto flight even though he did not have a confirmed seat.
She said he was very argumentative and, with a long line of impatient passengers behind him, she felt tagging the bag was the right thing to do.
The flight recorder was taken to India for examination
In the event, Mr M Singh never boarded the plane, but his suitcase was loaded and then transferred to Flight 182.
Ms Bakermans was taken to India in a bid to point out the man who had checked in the suitcase, but she was unable to identify him.
The Royal Canadian Mounted Police, or Mounties, thought they knew the identity of the bombers early on.
Vancouver-based Talwinder Singh Parmar, who led an extremist Sikh group called Babbar Khalsa, was arrested in November 1985, along with Inderjit Singh Reyat, a British citizen who once worked at the Jaguar car factory in Coventry.
But the Mounties were unable to link them to the bombing and both were freed.
Parmar was later killed by Indian police while Reyat, an electrician, was convicted in 1991 of building a bomb which was planted on another Air India plane, which exploded at Tokyo's Narita airport on the same day as Flight 182 killing two baggage handlers.
Reyat later made a plea bargain in which he admitted manslaughter in the case of Flight 182 and was jailed for five years.
The Mounties only made progress with Mr Malik and Mr Bagri in the late 1990s when they offered a reward of one million Canadian dollars.
Several witnesses came forward from the 100,000-strong Sikh community in British Columbia claiming that Mr Malik and Mr Bagri had confessed to playing a part in the bombing.
One key witness, who was given anonymity and placed in a witness protection programme, told the trial Mr Malik confessed to her.
She went on to say: "I could never hate him...I promised him, no matter what, I will always love you...I'll always be there to help you."
Mr Malik's lawyer, David Crossin, claimed she was lying and told the trial his client had no motive for planning the bombings and no interest in politics.
Mr Bagri's lawyer also claimed his client was innocent and claimed wiretap evidence - which the judge had ruled inadmissible - would have pointed to his client's innocence.
On Wednesday the pair were found not guilty of eight counts of murder and conspiracy by British Columbia Supreme Court Justice Ian Josephson.
The judge described the bombing as "fanaticism at its basest and most inhumane level" and concluded the devices had probably originated in Vancouver.
But he said the prosecution's witnesses were not credible and they had failed to prove the case against Mr Malik and Mr Bagri.
BOMBING OF AIR INDIA FLIGHT 182
The bomb explodes at 0714 GMT on 23 June 1985 in a suitcase packed into cargo bin 52-left. The explosion shattered a key bulkhead, sending the plane into a dive
The plane hits the sea, off the coast of Ireland.