Valuing Illicit Commodities – Getting It Right

As a Drug Expert Witness (DEW), you're regularly asked to give an opinion on the value of illicit commodities. How you reach that valuation and how you present it carries weight. The figures you provide often influence how the court assesses:

• The scale of the alleged activity

• The motive

• The wider context

• The potential benefit figure in POCA proceedings

Your valuation can significantly affect outcomes. Accuracy matters - for the court, for both sides in the case, and for your own professional standing.

Calculator + Price Guide does not = expert evidence

Where valuations go wrong

From our experience, common issues include:

• Inadequate training - at EWS, we dedicate a full day to teaching valuation and revisit it throughout the course.

• Overreach - sometimes, experts unintentionally go beyond their actual knowledge in an effort to be helpful.

• Over-reliance on price guides - especially those with unclear or outdated sources.

What's the issue with drug price guides?

Price guides circulate widely. Some are published by police forces, others by research bodies. Some are internal documents; others are public. A few may be useful - but many present problems.

Here's why caution is needed:

• Outdated figures - drug prices move fast. Many guides fail to keep pace.

• Unclear methodology - the source of the figures is often hard to trace. Who provided them? When? Under what circumstances?

• Lack of context - guides usually offer generic ranges that ignore local or case-specific factors.

• Assumptions over evidence - some are based on anecdotal input rather than direct observation or seized evidence.

Using a guide without understanding how it was produced can introduce inaccuracies. And in court, vague or speculative evidence doesn't stand up to scrutiny.

A recent example

One guide we reviewed recently quoted the price range of a kilogram of cocaine as £27,000 to £34,000 for the period October 2024 to March 2025. In our view, this figure does not reflect the market at that time.

We've submitted over 100 reports so far in 2025 for both the prosecution and the defence. We've seen multiple cases where kilograms were sold for well under £27,000 during that same period.

When we asked the authors of the guide to share the provenance behind their figures, we were initially told this would be provided. The response was later withdrawn, with the authors stating they do not disclose raw data unless compelled by a court.

That raises concerns. If provenance can't be shared, how can the figures be tested?

The same guide lists the price for an ounce of unadulterated cocaine as low as £800. We don’t dispute this; however, it contradicts the wholesale price. A kilogram contains 36 ounces, so 36 x £800 is £28,800. This provides very little markup on the kilogram price of £27,000. This creates an inconsistency that suggests one or both figures are wrong. In our opinion, the kilogram price in that guide is at least two years out of date.

Only the author of any price guide should provide evidence from it.

Why this matters

Published prices that don't reflect reality risk misleading less experienced experts, particularly when they claim to follow "NCA and UK police force practices." Unless the guide's authors genuinely have access to current, UK law enforcement data and sensitive information, which is unlikely, then this is misleading.

As expert witnesses, our duty is to the court. That includes upholding the Criminal Procedure Rules and helping the court deal with each case justly. Providing values that aren't supported by evidence runs against that duty.

The Criminal Procedure Rules require you to make clear:

·      What you know from your own experience

·      What you've drawn from others - and the limits of that information

If you're quoting external sources, be transparent. Qualify your opinion. And explain the limitations.

The Court of Appeal judgment in R v Pabon [2018] EWCA Crim 420 demonstrates what happens when an expert fails to do this. In that case, the expert didn't explain how he formed his views and gave evidence outside his area of knowledge. His evidence was found to be unreliable, and he was widely criticised.

The message is clear: don't give someone else's opinion as if it's your own.

If you don’t know, say so

It's fine to be cautious. Drug markets shift. Regional variations exist. If you've not seen a particular product sold recently, say so. If you're relying on case-specific evidence - like prices revealed in text messages or drug debtors/tick lists- use those.

If you use external data, explain where it came from and how you assessed its reliability.

For those instructing experts

• Only used credible experts with demonstrable experience in the case-specific aspects of the case at hand.

• Time spent on due diligence before instruction can save precious time and effort later.

• Push for clear, evidence-based views - not generic figures with no clear source.

Key points for expert witnesses

• Stick to what you know and what you can evidence

• Be transparent about sources and limitations

• Don't assume historical prices still apply

• Avoid using price guides unless you understand how they were produced, have the author's permission, reveal the use of them and can defend your actions at court

• Make sure everything you say in court is grounded in your expertise

Illicit drug valuations aren't about quoting numbers from a guide. They're about applying your experience responsibly and giving the court the best possible assistance. That's what's expected - and what the justice system relies on. Expert evidence is too important to get wrong.

(Those responsible for the price guide mentioned above were contacted for comment, but unfortunately did not respond. We would encourage them to either, i) reveal the provenance or ii) issue a retraction of the claims that they:

a)    “…have clear provenance and validation from multiple sources”

b)    “…published values are based on collated and validated data. In line with practices followed by forensic laboratories, the NCA, and UK police forces”)