CONFUSION reigns over the interpretation of forensic evidence in the courts, according to new a book which calls for a "logical" way of assessing expert evidence.
In Interpreting Evidence: Evaluating Evidence in the Courtroom, authors Bernard Robertson and Professor G Vignaux claim problems in cases involving scientific evidence "arise from problems of interpretation rather than experimental errors".
They add: "Where scientific evidence is misleading this is more likely to be because of a misapplication of the principles of inference than because of a technical failure in the laboratory processes."
The authors, who both hold academic posts in New Zealand, argue that evidence should be presented in a form of "likelihood ratio" which clearly expresses its value and "enables the court to combine it with other evidence in the case".
The book, praised by Dr Ian Evett of the Home Office Forensic Science Service, is part of the "new evidence scholarship" which has emerged in recent years.
Criminal barrister Sue Joshua, legal editor at John Wiley & Sons which published the book, said: "There has been a lot of discussion about this new scholarship in legal journals. It is essentially an argument about probability and errors in the presentation of evidence."
She added: "The book argues that there has to be an established logic which has to apply in all cases."
The book also looks at the value of DNA and blood tests and the inferences which are drawn from them.