Emily nearly lost access to her baby because of a hair strand test. Experts fear she's not alone
Getty ImagesWhen social workers asked a mother to submit a sample of hair for a drugs test, she thought it would prove she was clean and sober.
But it turned out to be the start of a legal battle to regain custody of her daughter.
Emily - not her real name - was a former ketamine user, whose habit had resulted in her baby daughter being taken into care at the end of 2022.
In the six months since then, she had made a determined effort to put her substance abuse behind her. With the help of a drugs charity, Emily had attended courses and taken urine tests about twice a week to prove that she was no longer using.
However, the result of the hair strand test came as a complete shock.
It stated that high levels of ketamine had been recorded, and there was evidence of active drug use over the six months up to June 2023.
As a result, the court refused Emily's request to be reunited with her daughter.
Hair strand tests are widely used in Family Court cases where parents are suspected of - or have a history of - drug or alcohol abuse. They can help judges make life-changing decisions, deciding whether it is safe for children to live with their parents.
The science of hair strand testing is sound, but there are growing concerns over the way tests are presented and interpreted.
Results can be affected by hair type, by the use of hair treatments or dyes, and by more individual factors, like the rate of hair growth and the environment you are living in. Critics say the test reports don't fully consider these factors.
For many years, reporting a case like Emily's was almost impossible, because of privacy rules governing Family Court proceedings. However, the Family Court has recently opened up its workings to journalists, and the BBC has been able to obtain a High Court order to tell her story.
"It absolutely blew me away," Emily says about the hair strand test, "because I hadn't touched [ketamine] at all."
She believed the traces of ketamine dated back to 2022, when she had still been a user.
The test report said the results demonstrated "active use of ketamine" since Emily's daughter had been taken into care. But more ambiguously, it said it could neither "confirm nor refute" that Emily had stopped using the drug.
Emily was not prepared to give up, and she volunteered to do six more hair tests as she fought for her daughter.
Hair strand tests for drugs and alcohol have become central to Family Court proceedings, and are carried out by government-approved commercial laboratories.
They work on the principle that when a drug passes into the bloodstream, it leaves traces within a person's hair. As the hair grows, it retains the traces and also provides a timeline of when the drug was taken.
To carry out the test, a sample of hair is cut into 1cm (0.4in) segments - the approximate length a hair grows in one month. The hair closest to the scalp will cover the most recent month, the next centimetre the next month, and so on.
The segments are broken up or mixed with solvents before being put through a chromatography process.
Results are then measured against the 'cut-off' level, which labs used to distinguish between active drug use and passive exposure. However, some in the legal community think it is too simplistic a measure to rely on.
Although it wasn't significant in Emily's case, some types of hair are more absorbent than others, and this can cause major problems, according to experienced family barrister Sarah Branson.
She recalls representing a young baby's father whose hair strand testing came back positive for crack cocaine - something that "didn't fit with the picture of the rest of his life".
She says the father was already caring for an older daughter, with no concerns from social services, and he had no history of using the drug.
However, her client had black dreadlocked hair. Branson found published academic research showing that because black hair - especially Asian, Afro-Caribbean or African hair - contains more melanin, it can absorb more drug traces.
It is possible he had absorbed the traces of cocaine from his environment.
In one academic study, black hair was found to be 15 times more absorbent than ginger hair. This meant that hair strand tests on two people with identical exposure to drugs might generate completely different results.
Other variables that can affect the results include the rate at which hair grows, the impact of different hair treatments and the environment where someone is living.
However, pressures on the current Family Court system mean that test results can be presented at a hearing without independent expert witness interpretation.
In 2024, the Court of Appeal overturned a lower Family Court decision to take three children away from their family based on hair strand tests. The lead judgment was given by Lord Justice Cobb, who is now president of the Family Division.
He said that the science was "sound" but the field was "evolving" and data should be treated with "proper caution".
A return to court
In February 2024, Emily made what she calls "a stupid mistake" and took ketamine once.
She owned up to this, but when the Family Court held its fact-finding hearing in December that year, hair strand tests indicated far more recent use.
A report covering the seven months from March to October 2024, said there was evidence of "repeated use" and that Emily's claim to have given up was not credible.
However, for this hearing, Emily had a new barrister - Jonathan Adler - who had done his own investigations into hair strand testing. The court had also appointed a respected specialist to appear as an expert witness.
Cross-examining this witness, Adler cited research suggesting other reasons for Emily's results, for instance, that ketamine at the ends of her hair could have been moved towards her scalp by the hair straighteners she had been using.
The expert conceded this point and admitted that Emily could have been telling the truth.
Other factors weighed in her favour, including clear urine tests and a positive parenting assessment from social workers. The local authority decided that Emily's daughter could come home.
We contacted DNA Legal, the lab that carried out the December 2024 test. It declined to comment, saying it was not at liberty to discuss matters.
A huge risk?
Adler believes a miscarriage of justice was avoided in Emily's case.
Barrister Sarah Branson says she represented parents in two cases where babies were placed for adoption after test results said they had used crack cocaine - which they denied. She believes she could now demonstrate those test results were flawed.
It can be very difficult for a social worker to challenge these tests. Wrongly dismissing a positive drug test could have disastrous consequences.
In 2023 Shannon Marsden and Stephen Boden were jailed for life for the murder of their baby, Finley. Finley had been returned to their care after they convinced social workers they were capable parents and had given up drugs. Hair strand tests showed they were still using cannabis.
There are now calls for forensic evidence in the Family Court to be subject to regulation, as it is in the Criminal Court.
"[It] would seem sensible to protect against risks of poor practice or risks to justice," says Prof Gillian Tully, the former forensic science regulator for England and Wales. "A huge part of doing forensic science well is making sure that the interpretation is right."
In December 2024 the most senior judge in the Family Court referred the issue of hair strand tests to the advisory Family Justice Council for urgent consideration, but it has yet to produce guidance.
The Ministry of Justice said it was aware of the concerns about hair strand testing, but that it was also awaiting the Family Justice Council's guidance.