Why Drug Traces Show on the Fingerprints of Non-Users

Author: University of Surrey
Published: 25 Mar 2018 - Updated: 30 Jun 2026
Publication Type: Research, Study, Analysis

Table of Contents:
Synopsis - Definition - Introduction - Main - Insights, Updates - Related Content

Synopsis: This research, conducted by the University of Surrey and published in Clinical Chemistry, found that class A drugs are now so widespread in the environment that 13 percent of drug-free volunteers carried traces of cocaine on their fingerprints, and one percent carried a heroin metabolite, despite never having used either drug. The work is useful because the team established a measurable "cut-off" threshold that reliably separates genuine drug use from everyday environmental contamination - even after the subject washes their hands or shakes hands with a user. For anyone subject to drug testing, including patients, employees, and people in clinical or legal settings, the findings matter because they support a non-invasive fingerprint test that can confirm a result was not skewed by ordinary daily contact.*

At a Glance

• 1 - The study tested fingerprints from 50 drug-free volunteers and 15 users who reported taking cocaine or heroin within the previous 24 hours.
• 2 - Cocaine is described as a common environmental contaminant already known to be present on many bank notes, which helps explain why so many samples tested positive.
• 3 - Researchers confirmed that cocaine and heroin can transfer through a handshake, yet the established threshold still distinguished true drug use from this secondary contact.

Topic Definition: Fingerprint Drug Testing

Fingerprint drug testing is a non-invasive method of screening for drug use that analyzes the sweat deposited in a person's fingerprint to detect substances such as cocaine, opiates, cannabis, and amphetamines. Unlike blood or urine samples, a fingerprint is quick to collect, difficult to falsify, and can identify the individual who provided it, making the approach attractive for clinical, workplace, and forensic use. A key challenge the technique must address is environmental contamination, since trace amounts of drugs like cocaine are present on everyday surfaces, which is why researchers set measurable thresholds to separate genuine drug use from incidental contact.

Introduction

Scientists have found that drugs are now so prevalent that 13 percent of those taking part in a test were found to have traces of class A drugs on their fingerprints - despite never using them. But there is no easy escape for users as researchers from the University of Surrey, who have previously developed a quick fingerprint test to identify users, have created a definitive way to prove the difference between those using cocaine and heroin, and those exposed to the drugs due to environmental factors.

Main Content

In a study published by Clinical Chemistry, researchers from the University tested the fingerprints of 50 drug free volunteers and 15 drug users who testified to taking either cocaine or heroin in the previous 24 hours.

Researchers tested fingerprints from the unwashed hands of the drug-free volunteers and, despite having no history of drug use, still found traces of class A drugs.

Around 13 percent of fingerprints were found to contain cocaine and one percent contained a metabolite of heroin. By setting a "cut-off" level, researchers were able to distinguish between fingerprints that had environmental contaminants from those produced after genuine drug use - even after people washed their hands.

To test the possibility of transferring drugs through a handshake, drug free volunteers were asked to shake hands with a drug user.

Fingerprints were then collected from the drug free volunteers after contact. Although cocaine and heroin can be transferred by shaking hands with a drug user, the cut-off level established allowed researchers to distinguish between drug use and secondary transfer.

Dr Melanie Bailey, Lecturer in Forensic Analysis at the University of Surrey, said:

"Believe it or not, cocaine is a very common environmental contaminant - it is well known that it is present on many bank notes. Even so, we were surprised that it was detected in so many of our fingerprint samples. By establishing a threshold for significance on a fingerprint test, we can give those tested the piece-of-mind of knowing that whatever the result of the test may be, it was not affected by their everyday activities or shaking hands with someone that had taken drugs."

Mahado Ismail, lead-author of the paper from the University of Surrey, said:

"It's clear that fingerprint testing is the future of drug-testing. There are many factors that set fingerprint testing apart - it's non-invasive, easy to collect and you have the ability to identify the donor by using the sample. Our study will help to add another robust layer to fingerprint drug testing."

The study was co-funded by Intelligent Fingerprinting, developers of the world's first commercially-available portable drug test that works by analysing the sweat from a fingerprint sample. According to Intelligent Fingerprinting's CEO, Dr Jerry Walker:

"this important study confirms the University of Surrey's position as one of the world's foremost academic research groups when it comes to fingerprint diagnostics using mass spectrometry. Critically, it also helps to establish a quantifiable high threshold for environmental drug traces - further establishing the validity of our commercial fingerprint-based drug test for cocaine, opiates, cannabis and amphetamines."

Insights, Analysis, and Developments

Attribution/Source(s): This quality-reviewed publication was selected for publishing by the editors of Disabled World (DW) due to its relevance to the disability community. Originally authored by University of Surrey and published on 25 Mar 2018, this content may have been edited for style, clarity, or brevity.

* Editorial additions by Ian C. Langtree.