Lennart Poulsen

Lennart is an international criminal barrister with an excellent reputation and over 15 years’ experience. He is recognised in the legal directories as a Leading Junior (Spotlight in Crime: International Criminal Law).

Lennart is regularly instructed to consult on some of the most high-profile matters and has extensive experience advising governments, international institutions and high-profile individuals. Recent instructions have involved advising Middle Eastern and African Heads of State and government ministers on matters of international criminal law and transitional justice. Lennart was the principal drafter of the underlying legal mandates, adopted by the Government of South Sudan in August 2023, for the establishment of its Commission on Truth, Reconciliation and Healing and Compensation and Reparations Authority. In May 2024, Lennart was engaged to contribute a chapter on a report, Libya: Voice of the Tribes, commissioned to support the peace and unification process for Libya. The final report can be read here.

He has defended in high-profile international cases including Prosecutor v Zupljanin at the International Criminal Tribunal for the former Yugoslavia (ICTY) and acted for several senior figures of the Jamaat opposition party in their defence for capital crimes before the Bangladesh International Crimes Tribunal.

Lennart is regularly sought after to lecture, speak at or chair panels at international conferences by the International Bar Association. He recently chaired an expert panel at a conference for the United Nations War Crimes Commission on the topic of universal jurisdiction. A recording of the panel discussion can be found here.

He has authored numerous articles for professional publications and for mainstream media on international law and recently featured in Counsel Magazine (the monthly journal of the General Council of the Bar of England and Wales) setting out his views on leadership in law.

Background and Expertise

Lennart has represented clients before various international criminal tribunals.  He also has extensive experience in preparing legal submissions before the ICTY, ICC, the United Nation Human Rights Council and various United Nations Commissions and Working Groups. Further, Lennart has prepared legal submissions on behalf of non-governmental organisations, high-ranking military commanders and senior government figures on matters relating to international criminal law and human rights, often within the context of a complex domestic and geopolitical backdrop and/or conflict area.

Lennart specialises in drafting complex legal documents and legislation including constitutional drafting and the legal mandate underpinning the establishment of truth and reconciliation committees as adopted in several African, Asian and South American countries.

Lennart is also highly regarded for his trial advocacy and has represented clients in criminal trials in the senior courts of England & Wales in matters involving major drugs conspiracies and serious violent and sexual offences.  He is a qualified and accredited Vulnerable Witness Advocate.

Lennart was selected in 2021 as one of a small group of successful applicants from across the Bar to take part in the Bar Council’s inaugural Leadership Programme – a landmark project requiring a 9-month commitment that resulted in a range of new leadership initiatives adopted and/or supported by the Bar Council.

In addition to his core international practice, Lennart was instructed as a junior for one of the Core Participants in the Grenfell Tower Public Inquiry on which he was instructed by DWF.

Prior to coming to the Bar, Lennart qualified as a solicitor at Clifford Chance.

Areas of Expertise

International Criminal Law

• Libya

Part of a team led by Steven Kay KC commissioned to produce the report, Libya: Voice of the Tribes.  Drafted chapter on the multiple failures of the United Nations to secure peace in Libya following the 2011 overthrow of the Qaddafi regime.

• Government of South Sudan

Led by Steven Kay KC. Provision of international legal services to cover advice upon international legal issues, conflict, the Revitalised Peace Agreement and transitional justice mechanisms. Principal author of the legislation underpinning the establishment of the Commission on Truth, Reconciliation and Healing and Compensation and Reparations Authority.  A key report ‘Pushing the Reset Button for South Sudan’ was drafted on the conflicts of 2013 and 2016 that challenged the currently accepted narrative within the international community including the UN, EU and African Union. He was one of the authors of a second report published in September 2023, ‘Setting The Record Straight’. Both reports are available here.

• Government of Egypt

Lead Junior led by Steven Kay KC advising President and Government of Egypt on allegations of international crimes. A series of reports were issued and received widespread acclaim. The reports are available at here

• International Criminal Technical Assistance Office

Advising a consortium of leading universities and practitioners on the establishment of a global International Criminal Technical Assistance Office for international criminal law cases.

• United Nations War Crimes Committee (UNWCC)

Part of ongoing work for the UNWCC advising on different aspects of international criminal law and current application of universal jurisdiction for international crimes. Chaired panel of experts at a UNWCC conference in November 2021 on Universal Jurisdiction, including Prof. Olympia Bekou (Professor of Public International Law, University of Nottingham); Tatyana Eatwell (Barrister, Doughty Street Chambers) and Marie O’Leary (Defence Counsel, International Criminal Court).  Among those in attendance was Chair of the International Bar Association, Dr. Mark Ellis. See link at

• Israel–Palestine conflict 2014

Co-drafted a preliminary report for the UN Independent Commission of Inquiry (COI) on the 2014 Gaza Conflict, on behalf of a Palestinian human rights group – in respect of war crimes allegedly committed by Israel during its military offensive against Gaza during the summer of 2014.

• Syria

Main author of a report, giving an overview of an investigation aiming to identify potential charges of crimes against humanity and war crimes allegedly committed by Syrian officials and military against the civilian population. The report was submitted to the Office of the Chief Prosecutor of the International Criminal Court (ICC) and to authorities in Spain, the UK and Germany.

• Bangladesh

Member of a London-based defence team led by Steven Kay KC acting for some of the most high-profile defendants of the opposition Jamaat party brought before the Bangladesh International Crimes Tribunal in Dhaka. Those accused were charged with war crimes and crimes against humanity during the 1971 Bangladesh War of Independence.