Mary Prior KC

Mary Prior KC is Head of 36 Crime, the criminal team of The 36 Group in London, and one of the most respected criminal silks practising at the Bar of England and Wales. A specialist criminal law barrister with more than three decades of experience, she has been named the Corporate INTL Global Awards 2026 “Criminal Law Expert of the Year in England”.

A leading criminal silk in England

Called to the Bar in 1990 and appointed King's Counsel (originally Queen's Counsel) in 2017, Mary Prior KC leads the criminal practice at 36 Crime. Her work covers the full range of the most serious criminal offences, including complex and organised crime, cybercrime, financial and corporate crime, murder and other violent crime, and serious sexual offending. She both prosecutes and defends, and is regularly instructed in cases where the issues, the volume of evidence or the vulnerability of those involved place exceptional demands on trial advocates.

She is particularly noted for her work with vulnerable people. Over the course of her career she has developed genuine expertise in cases involving witnesses and defendants who are on the autistic spectrum, who have ADHD or learning difficulties, who are affected by addiction, who have worked in the sex industry, or who have come through the care system. In serious sexual offence cases especially, the ability to question vulnerable witnesses, including children and those with special needs, fairly and effectively is central to a just outcome, and it is an area in which she is frequently instructed.

Judicial and leadership roles

Beyond her practice as an advocate, Mary Prior KC sits as a Recorder, hearing criminal and family cases as a part-time judge. This judicial experience gives her a rounded understanding of how cases are decided as well as how they are argued, an advantage she brings back to her advocacy. She is a Bencher of Gray's Inn, one of the four Inns of Court, reflecting her standing within the profession.

She has also taken on significant leadership within the wider criminal Bar. Having served as Vice Chair of the Criminal Bar Association, she became its Chair in 2025, a role that places her at the forefront of representing criminal barristers on questions of legal aid, court resources and the health of the criminal justice system in England and Wales. Her leadership comes at a period of sustained pressure on the criminal courts, making the advocacy she provides on behalf of the profession as important as the advocacy she provides in court.

Training, teaching and recognition

Mary Prior KC is a lecturer across all aspects of law and, in particular, on Rape and Serious Sexual Offences (RASSO). She is a trainer for the Midland Circuit and a vulnerable witness advocacy trainer, helping to raise standards among the next generation of criminal practitioners. Her contribution to the profession and to the advancement of women in law was recognised when she was named Woman of the Year 2020 in the Women in Law Awards.

Criminal advocacy at the highest level

Serious criminal trials in England and Wales test advocates in ways few other areas of practice do. Cases turn on the careful marshalling of complex evidence, the fair and skilful questioning of witnesses, and the ability to hold a jury's attention over lengthy proceedings while safeguarding the rights of the accused. Leading silks such as Mary Prior KC are instructed precisely because they combine forensic rigour with judgement and humanity, qualities that matter most where the stakes for individuals and the public are highest.

The Corporate INTL Global Awards 2026 “Criminal Law Expert of the Year in England” recognises Mary Prior KC's standing as a criminal law specialist, her leadership of 36 Crime, and her wider contribution to the criminal justice system through her judicial, training and representative roles.