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Piers Marquis is a committed criminal defence barrister, best known for defending allegations of murder, terrorism and offences related to serious organised crime.

He also specialises in defending allegations of “politically motivated” crime. His work in that area has led him to be instructed on behalf of numerous individuals and organisations in the ongoing Undercover Policing Inquiry.

He acts as Leading counsel, sole counsel and junior counsel, in cases of a particularly serious or complex nature and is consistently highly ranked as a Leading Junior in both the Legal 500 (Tier 1) and Chambers and Partners. In 2019 he was shortlisted for the UK Bar Awards, Criminal Junior of the Year.

What the directories say

“Piers is a very gifted and tenacious barrister. He has a great manner with juries as well as both professional and lay clients. His preparation is comprehensive and his tactical awareness is very acute. He is fearless in defending his clients and is not afraid of fighting their corner. This coupled with his ability to persuade juries is why he is very much in demand.” - Legal 500 2025

“His attention to detail and sheer hard work in delving in to the most minute material make him a formidable advocate.” - Legal 500 2025

“A brilliant advocate with a fearless approach. He is an out-of-the-box thinker, great with strategy and an excellent cross-examiner. He is also excellent at constructing and presenting legal arguments, both in writing and orally.” - Legal 500 2024

"Mr Marquis is a fantastic lawyer who possesses an astute legal mind and a passion for fighting for justice for his clients." - Chambers and Partners 2023

"Piers is very bright, hard-working and gets brilliant results. He cares about and has a very good manner with clients." - Legal 500 2023

"Piers is just a top barrister — hard working, committed, unflappable and totally dedicated to the cause. He has an excellent manner with clients and is respected by all for his professional, no nonsense approach in all of his cases. He can master and assimilate vast amounts of material." - Legal 500 2022

"He is exceptional with clients and knows the law well.” – Chambers and Partners 2022

"Thoroughly prepared and excellent with both lay clients and solicitors. Jury friendly. Fights for his clients with every sinew of his body and great passion." - Legal 500 2021

"Noted for his expertise in terrorism cases. Very client-friendly and a real fighter in court." - Chambers and Partners 2021

"He fights for his clients like there is no tomorrow." - Legal 500 2020

"An “outstanding” advocate who is praised for his “first-rate” commitment to his clients." - Chambers and Partners 2020

"Absolutely tenacious when on his feet." - Chambers and Partners 2020

"A born defender, his instincts and loyalties lie firmly with the individual." - Legal 500 2018

"A popular choice for Murder and Terrorism trials." - Legal 500 2018

"He brings a commitment to his clients and to court, which is rarely seen these days." - Legal 500 2017

"He has a natural empathy with clients, which assists him in understanding the issue at hand without compromising his professionalism." - Chambers and Partners 2017

"Just fantastic at anything from Terrorism to Magistrates trials." - Legal 500 2016

Piers firmly and passionately believes in the independence of the Bar and the right of individuals to receive proper representation when faced with prosecution by the state. Consequently since 2019, he has not been undertaking trial work under the Government’s AGFS Schemes 10, 11 and 12, which he considers to be an unacceptable continuation of a concerted effort to undermine the standards and independence of the Bar.

Recent briefs include murders, domestic and international terrorism, multi-million pound white-collar fraud, multi-national drugs importations/high end conspiracies to supply and cases arising from prolonged police operations targeting organised crime.

Details of his most recent and notable, successful defences can be found in the sections below, but include the acquittals of:

  • One of the Pentonville 3 Defendants alleged to have murdered a fellow inmate in prison.

  • Two Defendants, in separate unrelated trials, alleged to have been running “County Line” telephones alleged to have murdered drug associates.

  • A Defendant said to have attempted to murder a policeman by shooting him during a police chase in East London.

  • A British Bangladeshi, said to have been a member of an, Al Qaida/ISIS affiliated, armed group in Syria. He was alleged to have been a prime mover in the hostage taking of two Western journalists in Aleppo province; and one of those who shot them in the course of a failed escape attempt.

  • A Defendant said to have murdered a rival in a packed West End nightclub. The Defendant accepted being one of two men who shot and killed the deceased but maintained that he had acted in self defence.

  • A Bank Manager alleged to have orchestrated a multi-million pound fraud from a multi-national Bank, dispersing the proceeds through a complicated, international, layering process.

  • A Defendant alleged to have assassinated a rival drug dealer in an organised, point blank shooting outside the home of the deceased.

Piers also specialises in criminal work with a political and civil liberties dimension; with a particular emphasis on freedom of expression and the right to protest.

He was first instructed as leading counsel at only six years call, in the successful defence of one of the "Sequani Six" defendants, in what has been said to be the longest running animal rights trial in British legal history and the first effective trial under s.145 of the Serious Organised Crime and Police Act 2005.

He has defended prominent Trade Unionists, pickets, political activists, Animal Liberation Front activists, hunt and badger cull saboteurs/monitors, environmental and anti-arms trade protestors, Student and London “rioters” and was instructed in a large number of the Fathers4Justice cases. He secured the only acquittals in the Bristol Stokes Croft “Tesco Riot” cases and acted for defendants in the Occupy movement, including the occupation of Trafalgar Square and the eviction of the St.Paul’s camp.

He is instructed in the Undercover Policing Inquiry on behalf of a number of Non-State Core Participants, across all six tranches. His clients include the Campaign for Nuclear Disarmament, the Stop the War Coalition, a former Labour Member of Parliament and members of the Socialist Workers’ Party, Troops Out Movement, Youth against Racism in Europe and the Socialist Party. His opening statements to the Inquiry can be found here and here.

Before being called to the Bar, Piers gained considerable experience running the case preparation section in the criminal department of a solicitors’ firm in the Midlands. He also worked on civil actions against the police and cases involving gypsy rights.

He also travelled extensively around the world, funding his travels with work as a scuba divemaster, English teacher and journalist.

Homicide and Related Grave Offences
  • R v Butler and others – The Defendant was one of the “Pentonville 3” defendants alleged to have murdered a fellow inmate in the course of an armed confrontation following a feud over the control of prison contraband routes. Mr Butler accepted having been party to the confrontation, having taken a knife to the scene and potentially having at least injured the deceased but maintained that he had acted in self defence at all times and had had no choice but to arm himself in the face of an almost complete breakdown of order within the prison environment. The case had a political dimension because of the Defence emphasis on the austerity related cuts to the prison system funding that had led to Prison Officers lacking the resources to keep inmates safe from armed and organised gangs. After a three month trial the Defendant was unanimously acquitted by an Old Bailey jury. Press coverage surrounding the conclusion included: The Guardian and The BBC Initial coverage included: The Sun, The Mirror, The Independent, The Daily Star, The Express, The Daily Mail, ITV News. Huffington Post, Sky News and LBC. Ongoing trial coverage includes: The Times, The Dail Mail, The Telegraph, The Metro, The Guardian, The Evening Standard, The Telegraph and The BBC here, here, here, here and here.

  • R v Tyrone Henry – The Defendant was alleged to have attempted to murder a police officer by shooting him in the course of a police chase. Police evidence suggested that he had deliberately pointed the firearm at the officer before shooting him at close range. The Defendant maintained that he had taken possession of the pistol, which had been used in a shooting the previous evening, in order to prevent the escalation of a feud between associates of his. When tackled by the officers he dropped the firearm, which then inadvertently discharged having either come into contact with the ground or been kicked by an officer. The Prosecution dropped the attempted murder charge on the eve of trial and proceeded on a count of possession of a firearm with intent to endanger life. He was unanimously acquitted by an Old Bailey jury. Press coverage: BBC, Express, Metro, The Guardian, Standard, Telegraph, Sky News, Huffington Post, Mirror, Daily Star, The Times, and RT.

  • R v Walker and Allen – The Defendants were both charged with murder following a shooting in a crowded West End nightclub. The deceased was shot six times with two firearms. The immediate aftermath of the shooting was captured on venue CCTV, including footage of the Defendants running from the scene, each holding a revolver. The Defendant maintained that he himself had been targeted and shot by the deceased, had disarmed him and then shot him in the ensuing struggle. Hundreds of hours of painstaking CCTV examination by the Defence, established a credible case. The Defendants were both unanimously acquitted (Central Criminal Court). Press coverage: BBC, Mirror, Daily Mail, ITV, Sky News, Standard, The Guardian, Metro, Huffington Post, Channel4, Express, and Independent.

  • R v Mohammed Ahmed - The Defendant was alleged to have been running a “County Line” drugs telephone in to Sussex on behalf of South London gangsters. In the course of altercation over a drug debt he was said to have attacked the deceased and murdered him by stabbing him twice in the chest, in a public street in broad daylight. The Prosecution conceded at trial that contrary to their initial case, the Defendant had only armed himself in response to an armed attack by the deceased. The count of murder was not proceeded with. Press coverage: The SunITV News and The BBC here and here

  • R v Apire – The Defendant was charged with murder after the death of a drug dealer who died following a beating from the Defendant and another. The Defendant accepted having assaulted the deceased but maintained that the fatal injury was as a result of previous brain haemorrhaging, caused many months previously in an assault by others. He was acquitted of murder and manslaughter after successful submissions of no case to answer at the close of the prosecution case. Press coverage: ITV.

  • R v Valton and others - The defendant, charged with murder, was the alleged gunman in an organised gangland execution. The case concluded after a total of ten weeks of evidence including extensive examination of raw telephone data and cell site evidence and a history of tit-for-tat shootings. He was unanimously acquitted. (Central Criminal Court). Press coverage in the Daily Mail.

  • R v Sakyi – The defendant was charged with the murder of a bystander in an allegedly gang related shooting after a robbery in a night club. He was acquitted at trial. (Read more)

  • R v Stabler and others – The defendant, the former UK heavyweight kickboxing champion, was charged with two counts of Conspiracy to murder in a case described by the Crown as “vigilante terrorism”. He had allegedly sought to seek revenge against two men who had attacked and severely injured his best friend with a machete and a hammer. He was acquitted of the main counts at trial.

  • R v Laguda and another – The defendant was charged with Conspiracy to murder in an alleged planned shooting of a rival gang member. He was acquitted after successful submissions to exclude hearsay evidence. (Central Criminal Court).

  • R v Brooks – The defendant was acquitted of attempting to murder a passerby and an alleged rival gang member in the course of a south London shooting incident (Central Criminal Court).

  • R v Miller and others – The notorious murder of a passerby in a gang related shooting in a local shop. The defendant was said to have concealed the murder weapon for associate gang members. He was acquitted at trial (Central Criminal Court). (Read more)

  • R v Jeffries – Defendant charged with attempted murder having been seen by several witnesses to have stabbed the complainant, several times, to the head. After extensive disclosure arguments the Crown accepted a plea to s.18. The defendant avoided an I.P.P. and was sentenced to 3 years in custody.

  • R v McKinnon – Defendant charged with “one punch” manslaughter. He was acquitted at trial. (Read more)

  • R v M ­­– 15 year old defendant charged with the murder of another 15 year old during an altercation over a stolen mobile phone (Central Criminal Court). Press coverage in the BBC.

  • R v Dobson -  Defendant charged with murder after a north London shooting (Central Criminal Court). Press coverage in The Guardian.

Terrorism
  • R v J and others – The Defendant was charged with Terrorism offences focused on the hostage taking and shooting of two Western journalists in Syria.  The Defendants were alleged to have been members of an Al Quaida/ ISIS affiliated armed group, fighting in Aleppo province. One element of the Defence was that the group in question were, in fact, Free Syrian Army affiliates. The complex factual background of the Syrian conflict raised a number of legal complexities requiring consideration of jurisdictional issues and International Criminal Law. The case was discontinued at trial and not guilty verdicts were recorded. Press coverage: New York Times, Telegraph, BBC, The Times, ITV News, Channel4 News, Tehran Times, MSN News, Daily Mail, The Guardian, Fox News, CNN, USA Today, Daily Star, Huffington Post, and Wikipedia.

  • R v TB and others – The Defendants were alleged to have been involved in/with Rawat Al Tawheed, a sub group of ISIS fighting in Iraq and Syria and responsible for a propaganda campaign aimed at recruiting foreign Jihadists; charges included soliciting murder and preparing acts of Terrorism. Defence negotiations resulted in all terrorism charges against TB being abandoned shortly before trial. Press coverage: Daily Mail, Telegraph, Vice News, Standard, ITV News, BBC, and Mirror.

  • R v Heaton and others – Defendants charged with Terrorism Offences and Soliciting Murder after extensive police monitoring of political websites and internet forums. Defendant acquitted of all main charges.

  • K Solicitors v Metropolitan Police – Solicitors’ offices raided by police who seized large quantities of material under the provisions of the Terrorism Act in purported connection with the “Trans-Atlantic Airline bomb plot”. The warrant was ruled unlawful and legally privileged material was returned.

  • The Kurdish Lawyers Trial – International trial observer instructed by the International Bar Association’s Human Rights Institute in the ongoing trial, at the Silivri Prison complex in Istanbul, of a number of Kurdish lawyers alleged to have been members of the PKK.

International Crime
  • R v J and others – The Defendant was charged with Terrorism offences focused on the hostage taking and shooting of two Western journalists in Syria.  The Defendants were alleged to have been members of an Al Quaida/ ISIS affiliated armed group, fighting in Aleppo province. One element of the Defence was that the group in question were, in fact, Free Syrian Army affiliates. The complex factual background of the Syrian conflict raised a number of legal complexities requiring consideration of jurisdictional issues and International Criminal Law. The case was discontinued at trial and not guilty verdicts were recorded.

  • The Kurdish Lawyers Trial – International trial observer instructed by the International Bar Association’s Human Rights Institute in the ongoing trial, at the Silivri Prison complex in Istanbul, of a number of Kurdish lawyers alleged to have been members of the PKK.

Regulatory and Financial Crime
  • R v SA and others – Piers was Leading Counsel defending a Bank Manager accused of orchestrating a multi million pound fraud and dispersing the proceeds by way of a complicated, international layering system. After a four year investigation and an aborted trial listing, the Crown dropped the case following persistent Defence disclosure requests. Not guilty verdicts were recorded. 
  • R v E – The Defendant E was extradited from Spain in 2012, convicted of drugs importation offences and sentenced to 28 years imprisonment. The Prosecution instigated confiscation proceedings under POCA 2002 and in December 2015 secured a Confiscation Order in the sum of £13 million. A default term of imprisonment of 10 years was ordered, to be served consecutively to the 28 year sentence.

    The Defendant was able to re-open the proceedings by way of the slip rule. Piers was appointed to replace previous counsel and thereafter represented E in the re-hearing of the proceedings. Following the service of further financial statements and legal submissions on behalf of the defendant a Confiscation Order of just over £36,000 was made. A default term of 12 months was imposed.

  • R v McCourt and others - Multiple defendants involved in an extensive and complicated scheme to defraud the National Health Service in what police called “the largest ever NHS payroll fraud”. Piers appeared as sole counsel for the second defendant. All other defendants were represented by two counsel. McCourt was the only defendant to avoid a custodial sentence.

  • R v D and others – Defendant charged with laundering the multi-million pound proceeds of an International conspiracy to cultivate cannabis on an industrial scale. The case involved in excess of 100,000 pages of prosecution material.

Other Serious Criminal Offences
  • R v Pusey and others – Defendant charged with possessing firearms with intent to endanger life having allegedly threatened SCD19 firearms officers with a loaded MAC-10 sub-machine gun. He was acquitted at trial.

  • R v Gipson and others - Armed robbery and firearms offences. Defendant acquitted after a successful submission at the close of the Prosecution case.

  • R v S - Kidnap and child abduction. The defendant was charged with the kidnap of a child that he believed to be his. Extensive and eventually successful, abuse of process arguments as to the propriety of the CPS charging kidnap rather than child abduction and thereby depriving the defendant of a statutory defence.

  • R v H – Defendant assessed as having the cognitive function of a nine year old was charged with the rape of a vulnerable complainant. He was acquitted at trial.

  • R v MH – Defendant with learning difficulties charged with raping a neighbour. Acquitted at trial.

  • R v T – A teacher accused of sexually assaulting a teenage girl in front of a number of students. Acquitted at trial after defence research into myspace and facebook entries indicated that the allegation was a fabrication.

  • R v Rostas and others – The defendant was said to have been the “Fagin like” controller of an extensive conspiracy to steal. He was acquitted after a successful application to dismiss.

  • R v Clarke Grayson and others – Multi-handed conspiracy to commit cash in transit robberies. The defendant pleaded guilty after successful plea negotiations and was sentenced to two and a half years in custody.

  • R v M-B and others - Conspiracy to rob and kidnap with firearms. Defendant pleaded guilty after successful negotiations and avoided an IPP.

  • R v Saif and others – Multi-million pound importation of Class A drugs.

  • R v Brown and others – Prosecution arising from a two year police operation targeting cocaine supply in the West Midlands.

Protest Cases
  • R v Clark and others (The "Sequani Six") - Leading counsel on a Conspiracy under s.145 of the Serious Organised Crime and Police Act 2005. Anti-vivisection campaigners alleged to have mounted a sustained campaign against animal research laboratories and associated commercial enterprises. Defendant acquitted after a four month trial.

  • R v Jonathan May- Bowles (Jonnie Marbles) – Successful appeal against sentence of the comedian jailed for a custard pie “attack” on Rupert Murdoch. (Read more)

  • R v Keith Mann and Melvin Glintenkamp – Alleged Animal Liberation Front action indicted as a Conspiracy to burgle Wickham Laboratories resulting in the theft/liberation of 600 mice that had been subjected to Botox testing.

  • R v Kirk [2006] EWCA Crim 725, [2006] Crim LR 850, Archbold 2007 25-353 - anti-vivisection campaigner sending "indecent/obscene" material through the post

  • Currie and Cresswell v D.P.P. [2006] All ER (D) 429 (Nov), [2007] Env. L.R.D8, 171 J.P. 233, Archbold 23-51. – The defendant, alleged to have been the Animal Liberation Front’s “top bomber”, was charged as part of an alleged campaign to cause criminal damage to badger traps. The case involved extensive legal argument on Crown Immunity and the legality of the DEFRA badger cull. Appeal by way of case stated to the High Court.

  • R v Marcham and others – An allegation of aggravated trespass on the EDO arms factory in Brighton. Legal argument on the legality or otherwise of the Iraq War and the use of cluster bombs against military and civilian targets. The defendants were all acquitted at trial. (Read more)

  • Van Ek and Jukes v D.P.P - The defendants were charged with public order offences involving the alleged breaching of conditions imposed on demonstrations; arising out of the tented occupation of Trafalgar Square [2013] All ER (D) 109 (Read more)

  • R v Murray and others - The defendants were charged with offences arising out of the forcible police eviction of the Occupy camp at St. Pauls. Extensive legal argument on the proportionality of a criminal prosecution in such circumstances. (Read more)

  • Making Waves Prosecution - Defendants in inflatable, children’s “dragon” boats were charged with by-law offences having blocked the path of a Royal Navy frigate to prevent its access to the DSEi arms trade exhibition at London’s Excel Centre. The defendants argued that their actions were reasonable and necessary to prevent the proliferation of weapons being displayed by government sanctioned exhibitors without the requisite licences. They were acquitted at trial. (Read more)

  • R v Van Tonder and others - The defendant was charged with aggravated trespass having been part of the occupation of the main tower at Didcot Power Station. Legal argument as to the necessity of such action in the face of the increasing dangers of climate change. (Read more)

  • R v Risk, Downes and others - Fathers4Justice, the M4 santas, public nuisance. Defendants conditionally discharged at re-trial. (Read more)

  • R v Gorecki and others - F4J, the Vauxhall Santas. The defendants were charged with endangering the lives of rail users after occupying a railway gantry. Defendant acquitted at trial.

  • R v Wiffin - F4J, the Manchester Spiderman who occupied a crane at a building site in Manchester City Centre. He was charged with Public nuisance and acquitted after a successful half-time submission.

  • R v Redhead and Risk – F4J, Batman and Catwoman. Public nuisance and obstruction of the highway.

Criminal Appeals

Reported Cases      

  • R v Warren and others, representing the actor Ricky Tomlinson, in the successful appeal against politically motivated convictions arising from the 1972 Building strike [2021] EWCA Crim 413.
  • R v Johnson, Khan and multiple others (R v Johnson [2017] 4 WLR, 1 Cr.App.R 12, Crim LR 216)The post-Jogee guideline case of joint enterprise. 

  • R v Van Ek and Jukes [2013] All ER (D) 109

  • R v Pecco –  [2010] 7 Archbold Review 3, Archbold 14-34 - Identification, armed robbery, breaches of PACE and inadequate  judicial direction. Conviction quashed.

  • R v Modeste (A-G's ref No. 93 of 2007) [2007] All ER (D) 418 (Nov), [2007] EWCA Crim 3225) - Aggravated burglary, false imprisonment and sex offences. Sentencing.

  • Currie and Cresswell v D.P.P. [2006] All ER (D) 429 (Nov), [2007] Env. L.R.D8, 171 J.P. 233, Archbold 23-51

  • R v Kirk [2006] Crim LR 850, [2006] EWCA Crim 725, Archbold 25-353.