It is common for the secretary for justice to give detailed explanations of decisions not to prosecute or pursue further investigations in high-profile cases of public interest. But the one-page announcement of the decision not to prosecute former chief executive Leung Chun-ying was noteworthy for what it did not say. Secretary Teresa Cheng Yeuk-wah did not explain the legal principles behind the decision to drop a marathon corruption investigation, or follow the precedent of offering an independent legal opinion to support it. As a result she has come under unprecedented pressure from the Bar Association and the Independent Commission Against Corruption as well as a former director of public prosecutions, lawyers and pan-democratic lawmakers to provide a full public explanation. There is a compelling case for her to do so sooner rather than later to clear the air, for the sake of public confidence in the process and to be fair to Leung. Transparency is the strongest safeguard against controversy or lingering suspicion over the way it was handled. Lack of transparency is likely to fuel both. Missing Teresa Cheng must be seen to serve justice ICAC’s investigation of alleged wrongdoing by Leung in connection with a HK$50 million payment from an Australian engineering company which bought a firm of which he was a director lasted four years. Part of the payment, for a non-compete pledge, was made after he took office but allegedly not declared. Earlier this month ICAC said it would take no “further investigative action” after receiving legal advice from the Department of Justice (DOJ), which had decided there was “insufficient evidence to support a reasonable prospect of conviction” for any criminal offence. Now the ICAC has supported demands for an explanation to the public, with the agency’s advisory committee on corruption chairman Chow Chung-kong calling for “answers to the questions you have all raised”. He said investigators had “done their best”. And the Bar Association says the DOJ should seek a second opinion on the decision to drop the probe “to dispel any suspicion of favouritism”. An explanation of the DOJ’s reasoning and of the decision not to seek a second opinion is the least the public can expect.