But these amateur sleuths' interest goes beyond morbid fascination, demanding a grasp of biology, physics and chemistry. "With a bit of knowhow, students can make informed judgments about cases rather than accept what they read or see as gospel," explains lecturer Eira Hughes. "Murder mysteries and crime soaps have made forensic science fashionable and more accessible."
To capitalise on this, the class covers such techniques as footprint analysis, tyre prints and gun-shot residues. And where would a study of forensics be without poison? Arsenic, mercury and lead are on the syllabus, along with food fraud and forgeries, interspersed with gripping cases from the Victorian era to O J Simpson.
"I've attended conventional evening classes like flower arranging," explains Doris Calphas, 66, a former college bursar and fan of The Bill and The Coroner. "I was looking for something different which would not involve exams, something to tax my brain."
Tonight's topic is DNA fingerprinting, exploring gene inheritance, the chemical coding of molecules and the modern method for analysing DNA: laser fluorescence. "DNA can free or convict someone," Eira tells her captivated audience, "and is 90 per cent accurate. It has also been used to identify victims of major disasters such as air crashes."
Pauline Barnett, a social worker, says: "This subject helps me at work. One offender kept denying he was guilty, even though the evidence was overwhelming. I told him: 'There's only one person who has those fingerprints and that's you.'" Mary Hampshire
This class takes place at Ridge Danyers College, Marple, Manchester, and at other venues in the city. Contact the Workers Educational Association, tel: 0161 273 7652