Two years ago Derek Ogg watched his client Ross Monaghan cleared of a notorious gangland murder amid claims the police had undue influence on the forensic scientists in the case.
He believes such problems would not arise if Scotland followed the practice of England and Wales, where forensic services are not in the same building as law enforcement. Mr Ogg was speaking after it was revealed a report in to the Monaghan case by the UK Forensic Science Regulator is to be kept secret.
The QC believes the document - held up while the investigation of the murder of gang enforcer Kevin "Gerbil" Carroll is still under investigation - should be published.
He added: "Independence is as independence does. If you have your own building and your own command structure and the police need to make an appointment to see you, then you are independent.
"You can write all the protocols you like and have scientists doing fantastic work but if you occasionally have cases like Monaghan pop up, then you are going to have to answer questions about independence."
The QC was speaking just weeks after the main unit of Scotland's forensic science service, which answers to the Scottish Policy Authority (SPA) rather than the police, moved to the new Scottish Crime Campus from former labs at the former HQ of Strathclyde Police in Pitt Street, Glasgow.
Mr Ogg, a former prosecutor, said: "I don't doubt the good faith or ability of Scottish forensic scientists - but the institutional set-up could, no doubt very rarely, result in pressure being brought to bear.
"Jurors think science is perfect and science is certain. But scientists are not perfect and scientists are not certain: they are human beings."
The advocate said he preferred the English "entrepreneurial system" where private companies provide evidence to courts for both defence and prosecution.
He said: "The results have to be scientifically robust, your business depends on it. The public interest is simple There needs to be a robust firewall between police and forensic science."
Tom Nelson, Director of SPA Forensic Services, defended the current arrangements, which, after the opening of the multi-million crime campus look set to remain in place for years.
He said: "We believe that the crime scene to court model adopted in Scotland ensures independence and impartiality for all forensic-science disciplines and is preferable to the models adopted in other parts of the UK.
"It ensures a suitable degree of separation while also supporting the strong crime scene to court partnership that forensic science has with both operational policing and the wider criminal justice system in Scotland."
Mr Nelson and his service are delighted with their new dedicated wing in the crime campus, which provides a new state-of-the-art base free from the cramped confines of Pitt Street and another facility at Glasgow's Pacific Quay.
Forensic scientists share common areas with police and prosecutors at the Gartcosh campus. This, he says, enables them to work with their colleagues while defending their autonomy.
The SPA's predecessor, the Scottish Police Services Authority, which was abolished when the single force was created last year, backed such close co-location. Mr Nelson said they "concluded that there were significant benefits for the wider criminal justice system of having forensic services located with police, prosecutors and other key partners".