Pilot study launched to set new standards for cell site evidence

Forensic Science Regular Dr Gill Tully is to launch a pilot study to test the validity of cell site analysis amid

concerns about the way it is being used by police forces as evidence in court.

Dr Tully has announced that an unnamed number of UK forces and private organisations have now applied to be part of the

initial scientific trials that will act as a precursor to the formal pilot study for accreditation of organisations undertaking cell site


The timescale has been affected by the current lockdown, but the trials will be carried out as soon as possible, with the pilot

then able to proceed.

Speaking to The Investigator, Dr Tully said the work would lay the groundwork to demonstrate the reliability

(and any limitations) of cell site evidence.  It would enable a date to be set by which forces and companies would have to

demonstrate, through accreditation, their compliance with an international standard.

Explaining, some of her concerns around the current use of cell site analysis by investigators, Dr Tully told us: “Some of the

risks are around people not really being clear on the limits of their expertise.

I’ve heard examples where technicians have strayed into the area of giving expert evidence in court as it appears the

boundaries are not really clear about the difference between technical evidence and expert evidence.

“You might have a technician who has done some work and produced a map and that map will suddenly end up as evidence

in court, being interpreted by a police officer. Interpretation of scientific findings is opinion and evidence containing opinion is

admissible only as expert evidence. The witness giving the evidence must have the necessary knowledge and experience to

be recognised by the court as an expert.

Expert evidence

Dr Tully emphasised that she had ‘no issue’ with investigators or police staff taking on the role of expert witness in court but that

they must be clear about the difference between technical evidence and expert evidence.

“If they are going to be expert witnesses then they have to be operating within the specific framework for expert witnesses. This means they will have had to have the correct training and being compliant with the Criminal Procedure Rules Part 19 which set the framework for expert evidence.

“There is a whole set of legal obligations on expert witnesses. They have a unique position of trust in the criminal justice system and they are the only people allowed to give opinion evidence.”

Dr Tully also raised concerns around certain terminology and ambiguous phrases that were being used by investigators as part of evidence that could be misleading. She called on investigators to conduct more peer reviews of work and for training to address her concerns.

“If we use terminology such as ‘in the vicinity of’ but we don’t properly define that then it could be very misleading. It needs to be defined. If you’re going to use a vague term like that then you’ve got to define it.”

Unwitting bias

Similarly, she warned about using terminology such as ‘consistent with’ because that can be biased.

“If you say it’s consistent with the phone being at the location of interest then that’s a biased statement because if you are going to say that then you should be listing what else it is consistent with. It could be consistent with being at any other address within a mile’s radius.”

Dr Tully admitted she had read some reports that contained unwitting bias.

“The way some of the reports I’ve seen have been phrased does appear to be biased towards supporting a particular view-point. Phrases like ‘the phone of interest was most likely at or near the location of interest’ is not a balanced statement.

“It doesn’t make it clear what ‘near’ means. It doesn’t make it clear all the other places it could have been and where the limitations of the evidence are.”

Official guidance

Dr Tully spoke about the importance of forces and external providers being clear about what they are trying to achieve around cell site as evidence and about being clear how they are going to achieve this aim.

In a bid to provide guidance, Dr Tully produced an appendix to the Codes of Practice and Conduct. It sets out the good practice that practitioners are expected to follow now, and she also urges investigators to read and understand.

Here is the link to the appendix:


Annual report

Speaking in her annual report released earlier this year, Dr Tully called for gaps in quality to be resolved to prevent unreliable evidence being used in court.

The report also found that a digital skills shortage risks the sector falling behind criminals who are taking advantage of developing technology.

Dr Tully has reiterated calls for statutory enforcement powers to protect the criminal justice system. The regulator currently has no legal powers to enforce compliance with the required standards.

“The reality is that forensic science has been operating on a knife-edge for years, with particular skills shortages in digital forensics and toxicology,” she said.

“It is important that our ability to use science effectively in the criminal justice system does not lag behind technologically-enabled criminals.

Quality is not optional. Standards need to be implemented across the board if the sector is to learn from the past and improve for the future.”

The annual report provides an update on developments between November 2018 and November 2019 and sets priorities for the year to come. Issues include:

  • a lack of accreditation for CCTV comparison and a danger of experts straying outside their area of expertise

  • over 1,100 DNA profiles stored on the National DNA Database (NDNAD) have been confirmed as contaminated by police officers and staff, and are being removed

  • constraints on legal aid fees and a lack of enforcement powers have affected the ability of defendants to access quality-assured forensic science expertise


In July 2019, the Forensic Science Regulator launched the Anonymous Reporting Line. Run by Crimestoppers, it is available to the general public and forensic science professionals to report quality concerns.

For more information about the work of the Forensic Science Regulator, go to:


Dr Gill Tully