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Police forces across the UK successfully lobbied to use a face scanning system known to be biased against women, youths, and members of ethnic minority groups, following complaints that a more accurate version produced a reduced number of investigative leads.

How the System Works

British police utilize the national police database to conduct searches using historical face recognition. This procedure entails comparing a reference photograph of a person of interest against a repository of over 19 million mugshots to identify possible hits.

Admitted Bias

The Home Office conceded last week that the system was flawed. This acknowledgment followed a review by the National Physical Laboratory (NPL) found it misidentified people of Black and Asian heritage and women at much greater frequency than Caucasian males. The Home Office stated it “had acted on the findings”.

“It prompts the question of whether this technology only becomes effective if users accept biases in race and gender. Convenience is a weak argument for overriding fundamental rights.”

Known Issue

Internal documents show that this bias has been recognized for more than a year. Furthermore, police forces lobbied to reverse an earlier ruling that was designed to mitigate the problem.

Police bosses were informed of the algorithmic discrimination in September 2024. The Home Office-commissioned NPL review concluded the system was had a higher probability to suggest false positives for images depicting females, individuals of Black ethnicity, and those aged 40 and under.

A Policy U-Turn

In reaction, the National Police Chiefs’ Council (NPCC) ordered that the confidence threshold required for potential matches be raised to a point where the disparity was significantly reduced.

However, this decision was overturned the next month following complaints from police that the modified technology was producing a lower number of “investigative leads”. NPCC documents indicate the stricter setting cut the number of queries resulting in potential matches from 56% to a just under 15%.

Severe Disparities

Although the authorities refused to say what setting is currently used, the recent independent review discovered the system could produce incorrect matches for Black women almost 100 times more often than for Caucasian women at specific configurations.

The ministry commented on these results: “Our evaluation identified that in a specific scenarios the algorithm is has a greater tendency to incorrectly include some population segments in its match reports.”

Operational Effectiveness vs. Bias

Outlining the effect of the temporary raise to the system's accuracy setting, the police records note: “This adjustment significantly reduces the effect of discrimination across protected characteristics of race, age and gender but had a substantially detrimental effect on operational effectiveness”. The papers add that forces argued that “a once effective tactic returned results of questionable value”.

Broader Rollout Plans

Meanwhile, the government has opened a two-and-a-half-month public review on its plans to widen the use of facial recognition technology. The minister for police the relevant minister has labeled the tool as the “biggest breakthrough since genetic fingerprinting”.

Expert and Oversight Concerns

The chair of a police oversight board, head of the advisory panel for the police race action plan, said: “There was scant consideration in equality strategy sessions of the facial recognition rollout even with obvious cross-over with the plan’s concerns.

“These revelations demonstrate once again that the anti-racism commitments policing has made via the equality initiative are failing to be integrated into broader operations. Independent assessments have warned that new technologies are being implemented in a context where ethnic inequalities, inadequate oversight and faulty information gathering continue to exist.

“Any use of this technology must adhere to strict national standards, be independently scrutinised, and prove it reduces rather than exacerbates racial disparity.”

Home Office Response

A Home Office spokesperson said: “The Home Office treat the conclusions of the study seriously and we have already taken action. A updated software has been externally evaluated and acquired, which has no statistically significant bias. It will be tested in the coming months and will be subject to further assessment.

“The foremost aim is protecting the public. This gamechanging technology will assist officers to apprehend and prosecute offenders. There is human involvement in each stage of the process and no arrest or charge would be taken without specialist personnel carefully reviewing the results.”