Cheng Huan was born in Malaysia and educated in Singapore and England. At Cambridge University he gained a degree in law and a diploma in international law. Before commencing his legal career in Hong Kong he worked as a journalist for the Far Eastern Economic Review, Asiaweek, and was China correspondent for The Guardian newspaper in Britain. At that time he travelled extensively in China and wrote many articles on that country's affairs; he was the first person to report the death of Chairman Mao Tse Tung's second-in-command Marshal Lin Biao. In 1976 Cheng was called to the Hong Kong Bar. He was a deputy district court judge during 1986-1987. In 1988 he was made a Queen's Counsel.

Cheng Huan is one of Hong Kong's most well-known barristers, a lawyer famous for his sharp mind and friendly, effervescent character. Defending the Law is a tongue-in-cheek, witty recollection of his meandering route from journalism to a legal career. There are chapters on selected cases he has defended, each chosen to reveal the intense humanity of the criminal law. His story is packed with anecdotes, sincerity and good humour. The result is a book to interest both non-lawyers and lawyers alike. Courtroom life shifts swiftly from episodes of deep somberness to moments of great cheerfulness. The criminal law is revealed to be an arena of the most human emotions — desperation, resignation, love, excitement, amusement, and happiness. Cheng Huan is the archetypal defence barrister, a very human lawyer who is always on his guard not only to protect the innocent but also to defend the law itself from misinterpretation and misuse.

As Professor Wilkinson writes in his preface 'The book is full of gems that no one else would have written ... The book is packed with refreshing and delightful anecdotes in which the author demonstrates both his passion and compassion.'