One in 10 people have class A drugs on their fingertips, study says

Traces of cocaine or heroin were found on 13% of people who said they did not take the drugs

More than one in 10 people who have never used class A drugs may have traces of cocaine or heroin on their fingertips, forensic scientists say.

Researchers found tiny amounts of the illegal substances on 13% of volunteers who took part in a study after declaring they did not take the drugs.