The importance of forensic statistics
Forensic statistics is the application of statistics to forensic science and the law.
Broadly speaking, forensic science is the analysis of traces of evidence (such as body fluids, glass fragments, footprints and drugs) left at the scene of a crime by the criminal, victim or others. This evidence may be used subsequently to either implicate or exonerate a person suspected of committing that crime, or just to gain further insight into the incident. Over the years, with increasing technological advancement, forensic science has become a key part of criminal investigations worldwide.
But forensic science doesn't just involve identifying traces of evidence – sometimes it isn't obvious just what a piece of evidence really is. Other important questions that need to be answered are just how the evidence came to be at the crime scene, where did it originally come from, and who left it there. This suggests a natural role for statistics, as these questions can typically only be answered in terms of probabilities. So it is not surprising that the primary task of forensic statisticians is to evaluate any evidence found at a crime scene, so that this evidence can be appropriately presented to a jury in court. This task obviously carries great responsibility.
The advent of DNA profiling in the 1980s brought a big change in the way the legal system viewed quantitative data. Now a quantitative approach is being requested in many areas, far removed from the original area of DNA profiling. The earlier research and development work is being applied and further work is being done to tackle the increasingly more complex cases which arise in bringing a sound statistical approach to the assessment of evidence.

What does this career entail?
Please note first that forensic statisticians can operate under various guises (further details can be found in the "Who employs forensic statisticians?" section). At one end of the scale, there are people employed by forensic science units specifically to analyse forensic data; at the other end, there are some university lecturers who specialise in carrying out statistical research on forensic matters and act as consultant forensic statisticians when required. The methods of statistical analysis used will usually be similar, no matter where on this scale a forensic statistician is operating.
For an appropriate evaluation of evidence, a comparison of probabilities of the evidence under two different propositions is required. These propositions are usually those put forward by the prosecution and the defence. There are advanced statistical methods for doing this (for readers who are technically inclined, they are based on likelihood ratios or Bayes' factors). Much theoretical work has been done in the development of these methods. Calculations based on them might sometimes be fairly straightforward, though it also often turns out that there are non-standard issues to consider.
One example of casework that a forensic statistician may be involved with is DNA profiling, which is a powerful method of identification using genetics. Often, the evidence to be evaluated involves human (or sometimes animal) biological material such as blood, semen or vaginal fluid. Considerable work has been done in statistical and population genetics in assessing the importance of such evidence. Applications, however, are often not restricted to simple cases with one sample of DNA left at the scene of a crime and one suspect. Complications very often arise, for example because relatives may be involved, or the suspect may have been identified by a search through a DNA profile database, or the sample found at the crime scene may be a mixture of body fluids from more than one person. More advanced statistical methods are required in such situations.
Another role of a forensic statistician relates to sampling problems and determination of sample size. In some cases, it is necessary to examine a consignment of similar-looking items, and it is often not practical to examine every item. This may be purely on financial grounds but may be on health grounds also. The question then arises as to how many items should be examined on a sampling basis. For example, the consignment to be examined may be a set of CDs, some of which are thought to contain pornographic material. Then it is desirable for the examining officers to examine as few CDs as is commensurate with a good description of the proportion of the CDs which are illicit. The sample size determination is really just a quality control problem; there are UN Guidelines where the problem concerns drugs.
Finally, an important part of being a forensic statistician, as indeed it is for any statistician, is the ability to communicate results effectively to non-statisticians. Forensic statisticians are often required to attend court cases as "expert witnesses". This involves reporting calculated probabilities, or other statistical measures, to the jury, and explaining to them how the calculations were performed. This is a challenge in itself, as the jury will typically consist of people who have little knowledge of statistical methods, and is further complicated by the need to choose careful wording (so as not to "lead" the jury into a decision on guilt or innocence of a defendant).

Who employs forensic statisticians?
There is an increasing need for people to understand the role and application of probability and statistics in forensic science and the law. However, there are essentially no jobs and no career structure in forensic statistics in the UK as such.
The Forensic Science Service (FSS) of England and Wales has an Interpretation Group which considers problems of evidence evaluation, but it is small in size. In many cases, if the FSS wants help with a problem, it employs consultants. The Home Office has a Policing and Reducing Crime Unit which offers occasional contract work for statisticians to assist in particular projects. Individual police forces and law firms may also seek assistance with particular cases.
The area of DNA profiling is also growing. Although not strictly forensic statistics, there may be opportunities for statisticians in companies specialising in the analysis of DNA profiles for paternity and kinship testing.
The main route into a career involving forensic statistics is essentially as an academic, either as a university lecturer or specifically as a researcher. You would probably need to gain a lecturing or research post in a mathematics or statistics university department, and then pursue a research or consultancy path as part of your day-to-day work there. There are some research institutes that primarily focus on forensic science and statistics, notably the Joseph Bell Centre for Forensic Statistics and Legal Reasoning

What qualifications are typically required?
As we have explained above, it is often necessary to follow a career as an academic in order to be involved with forensic statistics, and the qualifications required for this are outlined on our career as a university lecturer page. For other positions, within forensic science units (UK-based or otherwise) or companies, an appropriate undergraduate degree is likely to be a minimum requirement, with postgraduate experience an advantage.
Continuing professional development
Forensic statisticians need to continue their personal and professional development. This can be done in several ways.
Most universities offer staff development programmes in which you may take short courses on almost anything, including computing software, presentational skills, management development and teaching skills. Even if you do not work in a university, at least some courses of a similar nature are likely to be available.
The statistical methods on which your work is based are also, of course, used in other application areas. You will probably find that there are conferences where the latest developments in these methods are explored; you might be able to submit papers or abstracts about your statistical work and attend the conferences, when you could have the opportunity to present your own papers as well as attend other presentations. Many conferences also have workshops in which you could participate. You are also likely to be encouraged to write up the statistical aspects of your work as formal papers for academic journals.
It will be extremely important to develop your communication skills, so that you can report your findings effectively to members of the police and legal professions, and all the more so if you will actually be appearing in court as an expert witness. It will also be important to gain some understanding of the legal system.
Your professional work as a statistician might well make it appropriate for you to seek the professional qualification of Chartered Statistician (CStat), which would give you a professional affiliation with the Royal Statistical Society.

Salaries and opportunities for advancement
As we have explained, work as a forensic statistician is likely to be on a consultancy basis, often coupled with a career as an academic. So there is, in effect, no salary structure attached to a career as a forensic statistician per se. General information about salaries in the academic sector can be found on our career as a university lecturer page. This also contains information about academic career structures and promotion prospects.

How to locate job vacancies for forensic statisticians
Again, the absence of a career as such means that there are unlikely to be advertisements explicitly for "forensic statisticians" as such, though there may be opportunities for statisticians and programmers within government or commercial forensic science and DNA profiling organisations. Any advertisements might appear in several places, including the following:
Daily newspapers (The Times, The Guardian and The Independent are probably the best).
The newsletter RSS NEWS of the Royal Statistical Society which is issued monthly to all members of the Society.
Electronic mailing lists (such as Allstat).
New Scientist.