Duncan qualified in 2003 and became a partner in 2011. He is a Law Society of Scotland Accredited Specialist in Medical Negligence (Defender) and is recommended by both Chambers & Legal 500 in that discipline. He has been described as "very experienced" and "highly regarded." Also, Duncan has been ranked in Professional Discipline by Chambers and has been praised by interviewees for his "client management and knowledge of the medical-legal aspects of the law." Others add: "He has a certain flair about him; everything's done efficiently and everything is succinct and well thought out."
In addition to court work Duncan also appears before various healthcare regulators including the Medical Practitioners Tribunal Service, General Dental Council and also the Health & Care Professions Council. He is a member of the Association of Regulatory and Disciplinary Lawyers and is recommended by Chambers Directory for his professional discipline expertise. His clients include medical and dental professionals, their unions and insurers.
Duncan defends medical product actions including trans-vaginal mesh and metal on metal hip implant cases. He also provides his professional negligence expertise to a variety of professions including accountants, insurance brokers and IFAs.
- Bell v Alliance Medical & Ors - 2015 CSOH 34 - eight-day clinical negligence trial involving multiple parties and disputes. The case raised interesting questions of indemnity and non-delegable duty in the healthcare sphere.
- SF v Quarriers - 2015 CSOH 82 - lengthy proof on timebar involving allegations of mistreatment in the 1960's. The pursuer claimed to suffer from dissociative amnesia. The case was not allowed to proceed.
- McDowall v G4S Care & Justice Services - 2015 SLT (Sh Ct) 129 - case involving alleged breaches of Articles 3 & 8 ECHR when a prisoner was restrained in hospital.
- Winn Pope v ES Access Platforms & Anr  CSOH 61 - personal injury case involving consideration of the concept of "control" under the Work at Height Regulations 2005.
- SL v General Dental Council - 2011 SLT 671 & 2011 CSOH 62 - Successful judicial review of a decision of the Investigating Committee of the General Dental Council to issue a warning.
- Copeland v Tenon plc (Aberdeen Sheriff Court, 11 Feburary 2011) - Successfully defending a claim for professional negligence against a receiver on the basis that the claim had prescribed.
- Quantum Claims v Wren Insurance 2011 SLT 671 & 2012 SLT 481 - representing the defenders in this case involving a dispute over the interpretation of a contract of legal expenses insurance.
- David Clarke v Argyle Consulting  CSOH 154. Succesfully represented the defenders in this case in relation to whether a complaint to the financial ombudsman interrupted the prescriptive period.
- Representing a global manufacturer of transvaginal mesh and tape implants in approximately 280 claims in the Court of Session.
- Representing healthcare professionals at all stages of the fitness to practise process before the MPTS, GDC, HCPC & NMC.
- Obtaining an interdict on behalf of a dentist being harassed by a former patient.
- Successfully defending a multi-million pound action against a general practitioner for an alleged failure to diagnose three spinal fractures.