EWJ August 62 2025 web - Journal - Page 25
County Lines Quantum –
A Flawed Algorithm
by Matthew J Atha BSc MSc LLB MEWI
Director – Independent Drug Monitoring Unit
Over recent years the use of mobile phones within the
drugs trade has become more sophisticated, with
drugs lines dedicated to the sale of particular drugs
increasingly common. These can include straightforward dealers acting alone to organised ‘county lines’
groups where the line phone is situated in a different
location to the sale of drugs. Although lines can supply a range of drugs, with the same principles applying, this article focusses on lines selling heroin and
crack cocaine.
Flaws in the Police Algorithm
Although the consumption figures are correct, it is
unsafe to apply this multiplier to each daily customer
of the drugs line for the following reasons:
1 The distribution of drug consumption does not
follow the normal ‘bell curve’ but is a one-tailed shape
with a large number of light users and fewer and
fewer heavier and heavier users, which results in average (mean) consumption far exceeding the median
(50th percentile), which comes out at 0.166g per day
combined (102mg heroin and 64mg crack cocaine per
day), such that 81% of crack cocaine users, and 75% of
heroin users, consume less than the mean daily average figure. This has two separate effects which increase the drugs line estimates:
The lines operate by collecting the phone numbers of
drug users, and advertising they are open for business
(‘on’) via bulk outgoing texts to their user base.
Users then contact the line to arrange deals, either by
meeting the dealer/runner in a designated place, or
delivery to their home postcode.
(a) Heavier users are more likely to purchase drugs in
larger quantities, e.g. 1/8oz at a time to last several
days, rather than in multiple £5-£10 deals from retail
drugs lines, saving considerably on the cost of their
usage.
To estimate the amount of drugs sold by a drugs line,
DI Harvey of the Metropolitan Police developed an
algorithm to analyse phone data and estimate the
number of customers using each line. He then multiplied this number by a figure for ‘average consumption’ of 0.9g per day (heroin and crack combined),
based on levels quoted in the report by Dame Carol
Black.
(b) Heavier and/or long-term heroin users are more
likely to be prescribed substitute opiates such as
methadone or buprenorphine (Subutex), thus reducing their demand for street heroin supplied by drugs
lines.
Although the source for Black’s figures are not clear,
the daily consumption averages for heroin, crack cocaine, powder cocaine and cannabis all fall within 0.1g
per day of ‘average daily use’ figures from IDMU
drug user surveys, noting these to have been quoted
in hundreds of court reports since the figures were
last updated in 2011.
EXPERT WITNESS JOURNAL
2 Furthermore, the algorithm presumes that all
customers of a particular line source 100% of their
drugs from that line, and never from rival lines. Even
in rural areas there is usually competition between
suppliers and users will tend to choose the line which
has availability at the time, can offer the fastest deliveries, and/or which provides the best value for money.
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AUGUST/SEPT 2025
