David Lammy MP has published a review into how people from ethnic minorities are treated in the criminal justice system.

Black, Asian and minority ethnic (BAME) people make up 14 per cent of the general population, but a quarter of the prison population, the report finds.

Four out of 10 young people in custody are from ethnic minorities, and this proportion has risen sharply over the last ten years. No one is sure why.

Are the differences down to institutional racism, or to the choices made by criminals? Frustratingly, we don’t think today’s report can answer this fundamental question.

The analysis

There is plenty of evidence of racial “disparity” in different parts of the criminal justice system, but not in every part, and it’s hard to attribute cause and effect.

In keeping with previous research, today’s review shows that people from minority ethnic groups tend to be arrested at higher rates than whites.

But after being arrested, they are slightly less likely to be charged by the Crown Prosecution Service than white suspects.

There’s no evidence that juries are biased against BAME defendants: they are found guilty at very similar rates to whites.

What happens at sentencing? One statistic which has received a lot of attention today is the fact that BAME offenders convicted of a drug offence are around 240% more likely to get a prison sentence than a white offender.

The figure comes from this Ministry of Justice analysis of sentencing by ethnicity in England and Wales in 2015.

It found evidence that people from different ethnic groups were indeed receiving different kinds of sentences, but not for every type of crime.

For crimes grouped under the heading “acquisitive violence” and for sexual offences, there was no difference in the odds of being imprisoned for white and BAME offenders.

The big difference was in drug offences. But the big limitation of the data is that we’re not sure if we are comparing like with like.

Apples and oranges?

While the researchers could account for some associations like previous criminal history, they couldn’t be sure they were comparing people who had carried out crimes of the same seriousness, or take into account the mitigating and aggravating factors that judges have to consider when they pass sentence.

The researchers said: “Drugs offences covers a wide range of offences, both in terms of class of drug and type of offence (eg from possession through to production and supply).

“Variations in the rates of imprisonment could potentially arise from variations in the mix of offences.”

“Variations in the rates of imprisonment could potentially arise from variations in the mix of offences.”

In other words, it’s unclear whether the BAME criminals included in this study were carrying out more serious types of drug offence.

Research in America has gone further in trying to allow for confounding variables. This US Bureau of Justice Statistics study tries to account for a wide range of differences in cases, and concludes: “Black males receive harsher sentences than white males after accounting for the facts surrounding the case.”

And this massive study by the Herald-Tribune newspaper into sentencing outcomes in Florida used a points-based system to compare blacks and whites accused of “the same crimes under identical circumstances”. It also found evidence of racial prejudice.

“Not guilty” pleas

One factor that accounts for some (but not all) of the difference in sentences for black and white criminals in Britain is the fact that BAME defendants are more likely to plead not guilty, and have their case tried by a jury.

This is important, as defendants who plead guilty generally get more lenient sentences from judges.

This trend would appear at first glance to be a matter of individual choice, rather than systemic racism, but the Lammy Review says: “The primary reason for this difference in plea decisions is a lack of trust in the (criminal justice system) among BAME communities.”

The suggestion is that people from ethnic minorities are less likely to believe legal advice they get from solicitors, or do not believe they will get a fair hearing from magistrates, so are more likely to take their case to a Crown Court.

It’s an interesting claim, but there’s no quantitative evidence in the review to back up the idea that “lack of trust” is the main reason BAME defendants are less likely to plead guilty.

The review cites this piece of research from the Centre for Justice Innovation – which repeats the claim, but also offers no hard evidence for it.

Phil Bowen, the director of the Centre for Justice Innovation, told FactCheck the “lack of trust” issue came up in “workshops and focus groups that we have done and other people have done” but said: “There is no one single broad survey that gives you that on a quantitative scale.”

The verdict

The Lammy Review contains a lot of statistics that point to different outcomes for people of different races in different parts of the criminal justice system.

But it cannot answer the six-million dollar question: is racial prejudice built into the system, or is something else to blame?

The statistical analysis that shows that ethnic minority criminals are 240% more likely to be jailed for drug offences than whites cannot exclude the possibility that the BAME offenders were simply convicted of more serious crimes.