Austerity cuts in the police force could lead to an increase in miscarriages of justice, a leading forensic scientist has warned, as constraints on funding lead to in-house forensic teams performing more selective tests.

Speaking at the Hay festival, Angela Gallop, who worked on cases including Stephen Lawrence, the Cardiff Three, the Yorkshire Ripper and James Bulger, said she feared the results of a cognitive bias in the police force, as they were both investigating criminals and performing forensic tests themselves, instead of employing third parties.

“I have got huge admiration for the police. Obviously there are some not so good officers among them but, by and large, I think they do a difficult job really well. Quite a lot of my career has been supporting the police,” she said.

“But they have been under the cosh with cuts and austerity, because forensic science is a very small part of their budget but a very large part of their external spend … it sticks out like a sore thumb. So when they’re thinking about cutting things, an easy thing to cut is their forensic science budget. To try and make up for that, they’ve brought more of the work in-house.”

When the Dogs Don’t Bark by Angela Gallop review – how a forensic scientist solves crime Read more

Gallop estimated 80% of forensic science had been taken in-house.

“I worry about cognitive bias,” she said, citing research by London University that found forensic scientists were more likely to find the results they were looking for if they expected to. “I can’t imagine an organisation of people, however good they are, can at the same time hunt down criminals and also produce impartial independent scientific evidence. I worry about that.”

When she started working in forensic science in the 70s, she was employed by the Home Office, she said. “How proud we were to be in the Home Office and not employed by the police – but that is not the case any longer.”

She said another direct result of austerity was that testing had become “commoditised”, meaning police asked scientists to perform fewer and more particular tests. “The narrower your focus in forensic science, the more likely you are to introduce a self-fulfilling prophecy. If you only test for certain things, you will only find certain things. The dangers are absolutely there, however good you are. It is a serious concern.”

On the cases she felt she could have contributed to, Gallop said she felt the parents of Madeleine McCann had been “badly served by forensic science, partly because some of it was done in a country that has got a little less structure than we have. But a little was done in this country, a very sensitive DNA technique was used, and I think it was overinterpreted. And I think that added to the problems”.

She also said she was “not at all happy” about the conviction of Brian Parsons, a Devon man who was found guilty of murdering Ivy Batten, 84, in 1987 after fibres from a hammer and gloves used in the crime were found in his car and coat. Parsons attempted to appeal his conviction several times but it was upheld in 1999. He served 15 years of a life sentence and was released in 2003.

“Interestingly enough, one of the lawyers involved, who later became a judge, has said in recent times that the one case he worries about is the Brian Parsons case. And the police force who did an investigation of the original police investigation, I know the chap who lead that, and he says he’s very worried about it because they could never pin it down.

“So if you get a judge and a police officer and a forensic scientist saying we think something is wrong with a case, then that is very worrying.”