Colmez worked for one year as a research assistant on Carol Vorderman's task force, commissioned by the UK government to study the state of mathematics education in the United Kingdom, and assisted with the presentation of the findings to the Joint Mathematics Council. She then became a mathematics tutor with a private tutoring firm, and with The Access Project, an organization that "helps disadvantaged children gain entrance into top universities". She is now a co-director of , an organization that helps students choose universities, and teachers track their progress.
Writing
With her mother, mathematician Leila Schneps, Colmez has co-authored Math on Trial: How Numbers Get Used and Abused in the Courtroom. This book, targeted for a general audience, uses ten historical legal cases to show how mathematics, especially statistics, can affect the outcome of criminal proceedings, especially when incorrectly applied or interpreted. While not written as a textbook, some reviewers have found it suitable for students, as an introduction to the topic and to "get them thinking, talking and even arguing about the issues involved", with another agreeing that, "they have struck the right balance of providing enough mathematics for the specialist to check out the details, but not so much as to overwhelm the general reader", and another finding the book suitable "for parents trying to support teenagers in their studies of mathematics - or in fact, law". While most reviews are positive, there has been some criticism that the book over-simplifies the influence mathematics has in complex trial proceedings. One reviewer finds that, while the book's description of the weakness of the mathematics is valid, that it does not completely treat the role mathematics plays in complex modern legal proceedings, while another suggests the book attributes insufficient weight to the counterbalancing practice of lawyers attacking opposing evidence and experts with their own.
In addition to the book, she has written guest columns in other publications on the same topic, and is a member of the Bayes and the Law International Consortium, which promotes improved understanding of the use of statistics in legal proceedings. In a recent interview she hinted that another book is in the planning phase, which will describe criminal cases where math was used correctly but was not accepted or understood by the judge or jury. In an online writer's publishing forum she has also experimented with a math textbook for teenagers presented in the form of a teenager's personal diary.
Public speaking
Since the publication of Math on Trial, Colmez has been an invited speaker at scientific education events in the UK. She has presented to the Conway Hall Ethical Society, the Cambridge Centre for Sixth-Form Studies, several shows for Maths Inspiration, including one at the University of Cambridge, and the 2014 QED conference. She has appeared on BBC Radio 4's Today Programme, discussing her book's subject of criminal trials in which math is used incorrectly or insufficiently, and on the BBC Radio 4 podcast, More or Less, discussing the same topic in relation to the Amanda Knox case.
