By Iblal IqbalPart of: Child Custody Specialists
A positive drug test does not automatically stop contact or mean a child is removed from a parent’s care. In family court proceedings, a hair strand drug test is expert evidence, so it is used only with the court’s permission, and only if the court decides it is necessary. The judge reads the result alongside everything else: what the levels can and cannot show, how recent any use was, and how any risk to the child can be managed. This guide explains what happens after a positive drug test in a child custody case, how hair strand testing works, and your options. It covers England and Wales.
Key takeaways
- No automatic outcome. The court decides what is best for the child, whose welfare is its paramount consideration (Children Act 1989, s.1).
- Testing needs the court’s permission. In children proceedings, nobody may instruct an expert or put expert evidence before the court without permission, and permission is given only where it is necessary (Children and Families Act 2014, s.13).
- Results are measured against cut-off levels. Labs use them to distinguish active use from passive exposure, and hair type, dyes and treatments can affect results (BBC, 26 May 2026).
- The court can decide who pays. It can give directions about an expert’s fees; otherwise the parties who instruct a single joint expert are jointly liable (Family Procedure Rules, r.25.12).
- Get advice before you respond to a request for testing or a positive result.
Positive drug test: what happens if you fail a court-ordered drug test?
A positive result is the start of a closer look, not the end of the case. In most cases:
- The court considers the result as evidence, alongside what each parent says, any Cafcass or local authority information and the rest of the evidence (s.1(3)).
- The risk to the child is assessed. The questions are how recent and how serious any use is, and whether it affects the child’s care.
- Safeguards are considered, such as supervised or supported contact or further testing over time, before any decision to stop contact.
- You can respond. You can explain the result, question the expert’s report and show what has changed.
What is a hair strand drug test and how far back does it go?
When a drug passes into the bloodstream, traces are left in the hair as it grows. For a hair strand drug test, the sample is cut into segments of about 1cm, roughly the length hair grows in a month, so the hair closest to the scalp reflects the most recent month and each further centimetre the month before (BBC). How far back a test can go therefore depends on the length of the hair sample.
The same technique is used for alcohol. Our guide to alcohol testing in family law covers that separately.
Cafcass hair strand test: who orders it?
Cafcass does not order tests itself. In private disputes between parents, a Cafcass officer may raise concerns about drug use in their advice to the court, but it is the court that decides whether testing evidence is needed, because instructing an expert and putting their evidence before the court both need its permission (CFA 2014, s.13(1) and (5)). When deciding, the court looks at matters including the questions the expert would answer, the impact on the timetable and the cost (FPR r.25.5). Evidence obtained without permission is inadmissible unless the court rules otherwise (s.13(2)).
If you have been asked about drugs or alcohol on the Cafcass call, our guide to preparing for a Cafcass interview explains how that call works.
If a test has been directed: before your sample is taken
- Tell the sample collector about any prescribed medication. Laboratories record disclosures made at collection, such as prescribed medications, in the report (AlphaBiolabs).
- Do not dye, bleach or chemically treat your hair before the sample, and mention any past treatments. Bleaching, dyeing, perming and straightening can affect the result (AlphaBiolabs), and one laboratory warns that attempting to tamper with results could lead the court to draw a negative inference (DNA Legal).
- Ask which substances and which period are being tested. The report lists the substances analysed and which were and were not detected.
- Ask for the full report, not only a summary of the result.
- Take advice before you comment on a result.
Whether the testing asked for is the right testing, and how to answer a result, are the points where a specialist’s view matters most.
Cafcass hair strand test results: how to read the report
Whether testing was raised by Cafcass, the local authority or a parent, the report sets out numbers and cut-off levels. The table explains how to read it in plain terms.
| What the report shows | What it can indicate | What it cannot prove on its own |
|---|---|---|
| A result above the cut-off level | Labs treat it as consistent with use rather than passive exposure | How the drug was taken, the circumstances, or the effect on the child’s care |
| A result below the cut-off level | Labs do not treat it as showing active use | That there was no contact with the drug at all |
| Results across several monthly segments | A pattern over time, such as rising, falling or stopping | Exact dates or amounts on particular days |
| Notes about hair treatments, dyes or hair type | Factors that can affect the result | Whether those factors explain a particular result without expert interpretation |
If you dispute a result, raise it early. Parties can put written questions to an expert about their report (FPR Part 25). In one judgment we covered, the court found that a mother’s positive results could be due to contamination; see court rules a mother’s positive drug test results could be due to contamination.
How reliable are hair strand tests?
The science is widely used, but there are concerns about how results are presented and interpreted. In May 2026 the BBC reported experts’ fears that hair strand tests are being misinterpreted in Family Court cases. It noted that results can be affected by hair type, hair treatments or dyes, rate of hair growth and the environment, and that in December 2024 the most senior family judge referred hair strand testing to the Family Justice Council for urgent consideration, with guidance still awaited at the time of that report (BBC). The British Association of Social Workers has also warned that drug and alcohol hair testing could be getting it wrong (BASW).
Problems have arisen before. GOV.UK has published information for people affected by hair strand testing carried out by Trimega Laboratories between 2010 and April 2014 (GOV.UK). A test result is one piece of evidence, and it should be read with everything else the court knows.
Can you refuse a drug test in family court?
If you do not want to take a test, the court will want to know why, and it will decide the case on the evidence it has. If you have a genuine concern, for example about how a test would be carried out or interpreted, say so clearly and get advice before you respond.
Can social services drug test you?
A local authority may ask you to take a test during an assessment or before proceedings. If a case is in court, the court’s permission is needed for expert testing evidence (CFA 2014, s.13). If you are asked to take a test, ask what it is for, who will see the result and how it will be used, and take advice before you agree. Our guide to social services investigations explains the wider process.
Can a parent lose custody for drug use?
Drug use can affect where a child lives and how they spend time with a parent, but there is no automatic rule. The court looks at the welfare checklist, including any harm the child has suffered or is at risk of suffering and how capable each parent is of meeting the child’s needs (s.1(3)). It will only make an order if that is better for the child than making none (s.1(5)).
In practice the questions are how recent and serious the use is, whether it affects the child’s care, and what has changed since. Safeguards such as supervised or supported contact, or further testing over time, can sometimes manage a risk without stopping contact. A care order can only be made by a court, and only if the threshold in s.31(2) is met.
Court-approved hair strand test cost: who pays?
There is no fixed price: the cost depends on the laboratory and the testing the court gives permission for. When the court gives permission, it can give directions about paying the expert’s fees and expenses, and it can limit the amount that can be paid. Unless the court directs otherwise, the parties who instruct a single joint expert are jointly and severally liable for the fees (FPR r.25.12). The cost of the expert evidence is one of the things the court considers before giving permission (r.25.5).
Frequently asked questions
Can the court drug test you without warning?
In court proceedings, testing is part of the case: a party applies for permission, the court decides, and it gives directions. You will know testing has been directed. If a professional asks you to take a test outside court, ask what it is for and take advice first.
Are hair strand tests court-approved?
There is no list of court-approved tests. What matters is whether the court has given permission for the expert evidence (CFA 2014, s.13) and how the court weighs the report alongside the rest of the evidence.
Will social services take my child if I fail a drug test?
A positive test does not by itself allow a child to be removed. Removal needs your agreement, police protection for up to 72 hours, or a court order, and a care order needs the s.31(2) threshold to be met. Social services and the court look at the risk to the child and how it can be managed.
Test directed or result back? Talk to us before you respond
A result read on its own, or from hair that had been dyed or treated, can be given more weight than it can bear. Before you agree to testing, reply to a report or accept that a result is right, book a free initial consultation with our child law specialists.
