Donna Louise Gray BSc (Hons), MSc (MedSci), DipFMS, AfCGI
Associate Director – Toxicology
Get to know the expert
Expert QuestionS & AnswerS
What kinds of cases or matters do you most often work on, and what makes you the right person to handle them?
I work on complex toxicology matters involving alcohol, drugs, medicines, chemicals, and other substances, with expertise in various types of investigations relating to impairment, toxicity, exposure, and causation. My multidisciplinary background spans forensic toxicology, scientific consultancy, R&D, and regulated life sciences. I have also provided specialist advice to governmental agencies in relation to occupational exposure and associated risk. This education, experience and training allow me to confidently opine in several areas of toxicology and exposure sciences.
What is one assumption people commonly make in your area of expertise that’s wrong, and what’s the actual reality?
A common misconception is that finding a substance in the body provides enough information to automatically explain what happened in the case. In reality, the presence of a substance does not necessarily mean impairment, toxicity, or causation. Toxicology is about interpreting the significance of a finding in context, taking into account concentration, timing, individual factors, and the wider circumstances of the case.
Tell us about a recent case or project where your specific expertise made a measurable difference to the outcome.
A recent project involved advising the UK Home Office Border Force, National Crime Agency, and police forces on the risks associated with emerging synthetic opioids. I provided toxicological and occupational risk assessments that informed evidence-based procedures, exposure controls, and safe-working practices for frontline personnel. By translating complex scientific data into practical guidance, the project supported operational decision-making and enhanced personnel safety.
What questions should clients be asking when they’re vetting an expert in your field — and what answers should they be looking for?
Clients should ask whether the expert’s experience extends beyond a single area of toxicology. While many toxicologists specialise in one aspect of the discipline, complex cases often require knowledge spanning multiple areas of the science. They should look for an expert who can apply toxicological principles across diverse scenarios, interpret findings within the wider context of a case, and deliver clear, independent, and scientifically robust opinions.
What separates a strong engagement in your area from a weak one, from your perspective as the expert?
A strong engagement starts with clearly defining the scientific questions and ensuring the expert has access to all relevant information. Toxicology findings must be interpreted in context, not in isolation. The best outcomes come from an objective, evidence-based approach and early expert involvement. Weak engagements often focus on a single finding or a predetermined conclusion, rather than a balanced evaluation of the available evidence.
Background
Donna Gray is a forensic toxicologist and expert witness with more than a decade of experience providing independent toxicological opinion in medico-legal proceedings throughout the United Kingdom.
As a member of Rimkus’ global Life Sciences team, Donna provides expert opinion in matters involving alcohol, illicit drugs, prescription medications, novel psychoactive substances (NPS), synthetic opioids, and other toxicologically significant compounds. Her expertise encompasses toxicological interpretation, evidential evaluation, impairment assessment, toxicity, causation, cause-of-death investigation, and expert witness reporting. She assists courts, coroners, tribunals, solicitors, and other legal professionals in understanding the significance, reliability, and limitations of toxicological evidence.
Donna’s experience spans both ante-mortem (living) and post-mortem (after death) investigations, including complex, disputed, and analytically challenging cases involving a wide range of substances, including antidepressants, antipsychotics, benzodiazepines, cannabis, cocaine, heroin, MDMA/ecstasy and opioids, in addition to anabolic steroids, pesticides, antifreeze, yew berries and toxic gases such as carbon monoxide and nitrous oxide. Throughout her career, she has authored more than 15,000 toxicology reports and provided both oral and written evidential assessments, including chain-of-custody evaluations, continuity-of-evidence reviews, and forensic integrity assessments based on analytical data checks. She is recognised for translating complex scientific findings into clear, balanced, and defensible expert opinions that support informed legal decision-making.
Donna has completed specialist expert witness training through Bond Solon, including Excellence in Written Evidence, Masterclass in Courtroom Skills, Witness Familiarisation, and Cross-Examination Testimony. She is committed to the highest standards of continued professional development, scientific integrity, independence, impartiality, and professional practice.
In addition to her medico-legal work, Donna has served as an independent scientific advisor to UK Home Office Border Force, working collaboratively with the National Crime Agency (NCA) and police forces across England. In this role, she has provided specialist toxicological and occupational risk assessment advice relating to emerging synthetic opioids, including fentanyl and its analogues (e.g. carfentanil, acetylfentanyl, and furanylfentanyl), as well as other high-potency synthetic opioids, namely nitazene compounds (a class of synthetic benzimidazole opioids, i.e. isotonitazene, metonitazene and protonitazenenitazene). Her work has supported the development of evidence-based operational procedures, exposure control measures, and safe working practices for frontline enforcement personnel.
Her broader professional experience includes analytical method development and validation, assay development, laboratory governance, quality management, regulatory compliance, and scientific leadership within highly regulated forensic and life sciences environments. She has also led the design, implementation, and management of an integrated quality and health and safety system within a preclinical research organisation operating within the pharmaceutical and biotechnology sectors.
Donna holds a high level of UK security clearance and combines extensive technical expertise with practical operational experience to provide scientifically robust, impartial, and defensible opinions in complex, high-profile, and legally sensitive matters.
Education and Certifications
- Forensic Investigation, 2.1 BSc (Hons): Glasgow Caledonian University (2013)
- Forensic Toxicology, MSc (MedSci) with Merit: University of Glasgow (2014)
- Forensic Medical Science, PGDip: The Royal Apothecaries of London (2016)
Associations and Memberships
- Professional Member: United Kingdom and Ireland Association of Forensic Toxicologists (UKIAFT)
- Professional Member: Society of Hair Testing (SoHT)
- Professional Member: The International Association of Forensic Toxicologists (TIAFT)
- Professional Member: The Institute of Traffic Accident Investigators (ITAI)