Justice must, at times, be tempered by mercy. The decision not to proceed with a third corruption trial for former chief executive Donald Tsang Yam-kuen is, no doubt, based on legal principle. But it is a merciful decision, too. Tsang, 73, suffering from poor health, has already endured two long trials on the same charge of unlawfully accepting an advantage while leader of the city. Two juries have listened to weeks of evidence and spent hours discussing the case. Neither has been able to agree on a verdict. The public interest would not be served by prosecutors seeking to convince a third jury of Tsang’s guilt. Indeed, such a course might be seen as an abuse of the court process. The Department of Justice is right to bring these proceedings to an end.

Tsang’s first trial ended in February. He was jailed for 20 months for misconduct in public office after failing to declare his interest in a retirement home in Shenzhen. But the jury in that case could not agree whether he was also guilty of another charge, of accepting the free refurbishment of the penthouse, worth HK$3.8 million. In return, he was alleged to have been “favourably disposed” towards radio station Wave Media, whose majority shareholder owned the property and paid for the renovation.

A second trial on the bribery charge ended last week with another hung jury. The prosecution could have sought a third trial, but this would only be permitted in the most exceptional cases. While the corruption charge is serious, carrying a maximum prison sentence of seven years, the evidence presented by the prosecution was largely circumstantial. Corruption is a notoriously difficult crime to prove. Jurors can only find Tsang guilty if they are sure, beyond reasonable doubt, that he committed the crime. Two juries have not been convinced. The evidence presented has not, however, reflected well on Tsang. The public will wonder about the true nature of his dealings with Wave Media shareholders. He chose not to go into the witness box to explain. This is his right, but it leaves questions unanswered. Tsang is, however, innocent until proven guilty. And guilt has not been proved on the bribery charge. The prosecution’s decision must be respected. Tsang is currently on bail pending appeal against his conviction and sentence for misconduct in public office. Depending on the outcome of that case, he may yet return to prison.