Dr Marsh has worked as a Senior Research Fellow in the Social and Behavioural Research Unit since 2010. Her research is focused on providing evidence for policies to achieve New Zealand’s Smokefree 2025 goal. Her particular field of interest is reducing the supply of tobacco, and in particular commercial retail availability. More recently her work has concentrated on the spatial location of tobacco retailers in New Zealand, using geospatial analysis to identify retail regulation policies to reduce availability, while considering the equity impacts.