How a murder and a bombing cleaned up DNA profiling
The UK pioneered a forensic process to identify suspects from tiny amounts of DNA, but occasional flaws had big consequences. Andy Extance pieces together the whole story for the first time
Low copy number (LCN) DNA testing was introduced in 1998 to deal with cases where there was very little DNA material available. DNA profiling relies on the polymerase chain reaction (PCR) method, which copies DNA in forensic samples, boosting it to measurable levels. The LCN test pushed this amplification to its limits, but scientists had seen that this sometimes stopped the test from working properly. The technique was used to solve the murder of Rachel Nickell, but a case involving a terrorist bombing in Northern Ireland highlighted different issues with the LCN method. This is the first account to bring these events together and show how they drove forensic scientists to refine their techniques.