Siôn is a specialist criminal practitioner focusing on serious crime, including murder, manslaughter, serious sexual offences, serious violence, fraud and drug conspiracies.

Siôn is instructed to prosecute and defend serious criminal cases and is a Category 4 prosecutor for the Crown Prosecution Service.

Siôn has also developed a particular interest in firearms offences. He was instructed by North Wales CPS as the junior in the trial of Fitzsimmons and others (manslaughter by gross negligence) and has prosecuted and defended a number of criminal cases involving the use of firearms.

In addition, Siôn regularly appears on behalf of Police Authorities in opposing Shotgun and Firearms appeals before the Crown Court.

Siôn is a fluent Welsh speaker and frequently conducts trials and conferences through the medium of Welsh.

Operation Blue Lancelot (2020-2022): Leading counsel in prosecution of 22 individuals for conspiring to supply class a drugs.

Jones and Mitchell (July 2021): Prosecuting junior in Murder/Manslaughter case.

Operation Awakening (2021): Prosecution in conspiracy to burgle – Liverpool Crown Court.

Operation Blue Fedora (2020-2021): Defended in large scale conspiracy to supply Class A drugs.

R v. Fitzsimmons and others (2018-2019): Prosecution in a case of Gross Negligence Manslaughter.

R v. Jordan (2018): Successful prosecution murder case.

R v. Konopka (2018): Successful Defence in a conspiracy to blackmail.

R v. Keith Jones (2018): Defending in a large scale bus conspiracy to defraud.

R v. Barnes October (2017): Successful defence in a conspiracy to defraud.

Regina v. Zack Davies: Prosecution of a white supremacist with Attempted Murder.

Regina v. O’Connor and others: Prosecution of 5 defendants in a false imprisonment/robbery/kidnap/section 18 wounding.

Operation Yonside – Regina v. Paul Hughes: Defending in major North Wales drugs conspiracy.

Operation Measure – Regina v. Leon Thomas: Defending in North Wales drugs conspiracy.

Regina v. Julius Hecko: Defence junior in murder.

Regina v. Owen and Williams: Prosecution of two drivers for causing death by dangerous driving.

Regina v. Lukasz Reszpondek: Prosecution junior in murder.

Regina v. Thomas Blue: Prosecution junior in Murder.

Bar Vocational Course Cardiff University 1997-1998

LLB Exeter University 1994-1997

Ysgol Maes Garmon

Criminal Bar Association

Category 4 prosecutor

Former Joint Secretary of Legal Wales

Chester representative over 14 years call on the Management Board of the Wales and Chester Circuit