A source at the Ministry of Foreign Affairs has demanded justice for the murder of a Saudi citizen in Thailand whose case was dismissed earlier this year by a Thai criminal court due to lack of evidence.

Mohammed Al-Ruwaili, a Saudi businessman, had traveled to Thailand in 1989 to investigate the theft of gems worth $20 million belonging to the Saudi royal family, only to be abducted and killed in what became known as the “Blue Diamond Affair.”

“The Saudi government does not wish to interfere in the internal affairs of other countries,” said the ministry official.

“While the Kingdom does not question the fairness of the judicial system, the Saudi government takes issue with what happened during the trial.”

“The judge presiding over the case had been replaced right before sentencing,” he said. “This, coupled with negative political influence, paved the way for meddling in the country’s judicial system and, as such, in the final outcome of the trial.”

Three Saudi diplomats were shot execution-style in Bangkok days before Ruwaili vanished in 1990 and Saudi Arabia has long suspected official involvement in the killings.

“This also indicates that the Thai government had not done enough to resolve the mystery surrounding Al-Ruwaili’s assassination and that of three other Saudi diplomats, nor has it done enough to bring the murderers to justice,” he said.

“We urge the Thai government to do what is right in this case and put political factors aside,” he said.

A Thai court had dismissed a case against five men who were accused of kidnapping and killing Ruwaili, including a senior police officer, on March 31 after a criminal Court ruled there was insufficient evidence to try the men.

The gems and jewelry had been stolen from a Saudi prince’s palace by Kriangkrai Techamong, a Thai gardener, who shipped the loot back home to Thailand.

Kriangkrai was arrested soon after, but had already sold many of the stolen gems, including a 50-carat blue diamond. Some of the jewels were eventually returned to their owner, but the Kingdom later said that most of the returned gems were fake.