Julian Perry Robinson, who has died aged 78, combined academic research with behind-the-scenes advocacy to enhance controls on some of the most inhumane weapons in the world. His focus was on issues related to chemical and biological warfare (CBW) and the international efforts to eradicate the use or possession of such weapons.

In the late 1960s, with cold war differences between the major powers on the control of biological weapons, he examined the challenges of CBW in factual terms rather than the rhetoric of the time. A key concept Julian promoted – that all disease-causing organisms and the toxins they produce should be considered biological weapons, unless held for clearly peaceful purposes – became the core of the 1972 Biological Weapons Convention, the first treaty to ban a whole class of weapons of mass destruction. This concept, which became known as the “general purpose criterion”, has meant the convention has not been overtaken by scientific and technological developments.

As a leading member of the specialised study groups within the annual Pugwash conferences for scientists interested in international security issues, he was able to bring experts and policymakers from east and west together in informal settings. Julian helped generate the common understanding in the Geneva negotiations that resulted in the Biological Weapons Convention.

He was also a member of the expert groups advising the UN secretary-general and the World Health Organization (WHO) on CBW issues, and was the anonymous lead author for influential reports from each, but the most visible aspect of his work at this time was his contribution to The Problem of Chemical and Biological Warfare, a six-volume study published between 1971 and 1975 by the Stockholm International Peace Research Institute (SIPRI) and still regarded as a classic text in the field.

It was symbolic of the growth in his reputation over time that while the 1970 WHO study Public Health Response to Biological and Chemical Weapons – WHO Guidance was published anonymously, the 2004 follow-up explicitly named Julian as executive editor. Embodied in this work is the concept that the best counter to deliberately caused disease (which is what biological weapons are tools for) is to have effective measures against naturally occurring disease. Julian’s death from Covid-19, an infectious disease the spread of which might have been limited with more effective measures, is thus a bitter irony.

The adoption of the Biological Weapons Convention moved the international focus to the need for a Chemical Weapons Convention, but this took a further two decades to negotiate. Julian was used as a trusted resource by officials from many governments. International treaties require national implementation. Julian provided briefings that were quoted during the parliamentary debates on the bill that brought the convention’s provisions into law in the UK. The briefings prevented a weakening of the UK’s national provisions. The resulting Chemical Weapons Act of 1996 established a government advisory committee to which Julian was one of the first appointees.

The son of Marguerite (nee Downing) and John Perry Robinson, Julian was born in Jerusalem, Palestine, where his father was a British official with the Mandate government. He attended Canford school in Dorset, and had an early interest in chemistry – his sister, Harriett, recalled him setting off colourful home-made smoke bombs as a teenager. He went on to study the subject at Oxford, graduating in 1964. His dissertation title was Some Aspects of Chemical Warfare: An Investigation into the Influence of the Second World War on the Development of Chemistry, With Particular Reference to the War Gases, an early indication of the path his career would take.

He studied national and international patent law with Kilburn & Strode Chartered Patent Agents in London from 1964 to 1968. The twin perspectives of chemistry and law provided him with insights into how effective legal constraints on CBW could be constructed.

Julian’s early career, from 1968 until 1971, was in Sweden at SIPRI, where he met his partner Mary Kaldor. In 1971, they both moved to the University of Sussex and joined the Science Policy Research Unit (SPRU), which became a leading centre of study on CBW issues. Julian cemented a long-time research partnership with the Harvard University biologist Matthew Meselson through the establishment in the 1990s of the Harvard Sussex Program, which they co-directed.

At Sussex, where Julian was appointed professor in 2001, he created a unique archive which underpinned the evidence base of his work and which remains as a legacy of his insights. This extensive archive attracted scholars from around the world as well as benefiting his own research students – many of whom moved on to key positions in academia and inter-governmental organisations.

The rigour of his scholarship gave him confidence in challenging established assumptions or spurious policy positions. In 1981, when the US accused the Soviet Union of contravening the Biological Weapons Convention by supplying and using a biological weapon dubbed “Yellow Rain” in south-east Asia, Julian and Meselson were able to show that the observed phenomenon of yellow spots falling from the sky came from hives of bees collectively defecating from above the tree level. This episode illustrated the need for careful analysis in an area rife with propaganda and unresolved accusations.

Seemingly effortlessly polite, Julian could calmly deconstruct flawed arguments with precision even when other participants in a meeting were heated. Yet he was a hesitant public speaker and would avoid media appearances whenever possible.

He officially retired in 2007 but maintained an office in his archive at SPRU. Recent work included compiling a chronology of relevant evidence relating to chemical weapons use in Syria. He continued publishing – most recently a detailed study of the novichok series of chemical weapons.

He is survived by Mary, whom he married in 2008, and their two sons, Joshua and Oliver; by his son, Charles, from his first marriage, to Nina Hargreaves, which ended in divorce; by five grandchildren; and by Harriett.

• Julian Philip Perry Robinson, chemist and lawyer, born 11 November 1941; died 22 April 2020