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The History of the Magnifying Glass in Forensic Science

Sherlock Holmes epitomises the forensic use of the magnifying glass in criminal investigations. Along with his pipe and intuition, it has always been a staple tool in the fictitious detective’s armour of accessories.




While Holmes and his ever-present companion Doctor Watson were dreamed up by Sir Arthur Conan Doyle in 1887, the magnifying glass has been around for a lot, lot longer.


In fact, the tool dates as far back as the ancient Egyptians. They first used pieces of crystal to enlarge the optical view of tiny objects. Later, gemstones were used to allow the rich and powerful to better see live performances of theatre.


However, the world can thank the English for inventing the first optical magnifier used in science. Roger Bacon, a philosopher, is credited with the advancement in the 13th century.


His invention would serve as a forerunner to the compound microscope.


However, the simple, hand-held tool has solved many a crime – and long before the discovery of DNA and its applications in forensics.


While widely used by detectives, the magnifying glass did not form an official part of police kit in the UK until the early 1900s.


It was at this time that fingerprint technology was coming into its own, having proved its worth in new classification systems developed in the latter part of the 1800s. The first successful prosecution for murder based on fingerprint evidence in the UK involved bungling burglars and brothers Alfred and Albert Stratton, who were convicted and executed in 1905.


Although considered a revolution at the time, fingerprints had been used to identify people in China for thousands of years. A database of criminals’ fingerprints was established in the US in 1896.


The magnifying glass and microscope were used to manually distinguish unique fingerprint ridge features until digital technology overtook much of that work.


Double convex optical lenses are what make the magnifying glass ‘work’. The combination serves to enlarge an object when the glass is placed close to the item being viewed. It achieves this by bending rays of light into the centre of the glass or lens.


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