"Justice is truth in action." These words spoken in 1851 by Benjamin Disraeli encapsulate the ultimate objective. The moment justice is partisan, truth becomes a victim, and a core element of any democratic society is fatally undermined. Miscarriages of justice provide prime examples of how easily individual errors and misdemeanours translate into systemic abuse unless there is constant awareness and scrutiny. Such vulnerabilities have to be identified and circumscribed by a regularly reviewed and effective process of checks and balances.

It is tempting to believe that the infamous miscarriages of the 80s are a thing of the past, and that the incorporation of various legislative instruments and organisations have eliminated the risk of repetition. Unfortunately it never works like this and each generation has to relearn the lessons of the past and build on the earlier remedies. While wrongful convictions based on confession evidence are now rare to nonexistent, the focus of evidential attention has become forensic science. The problem in both instances is the same: the growth of a culture in which there is an arrogance of unquestioned presumption and assumption.

The UK is one of the few major nations not to have a national forensic science institute and, in the wake of government market-based policy, no longer has a national forensic science service. The main repercussion of these deficiencies is fragmentation and creeping deregulation. Unless standards are unified, certified and monitored, unprofessional practices arise as do unprofessional practitioners.A recent series of events exemplify the urgent need for re-appraisal. This month Dr Freddy Patel, a pathologist who had provided the initial opinion following the death of Ian Tomlinson in the 2009 G20 protest, was stuck off by the Medical Practitioners Tribunal Service. The panel found that he had an arrogant mindset that generated an unwarranted confidence in his own ability. He had committed 68 errors in his examination and had wrongly attributed Tomlinson's death to cardiac arrest. The panel also found that he had lied about his status in order to remain on a Home Office register.

If this were an exceptional aberration by a novice that slipped through the net it would be serious enough, but the malaise runs much deeper. Patel had been qualified for 35 years. Significant concerns about him had been voiced before 2009. These had seen him removed from the Metropolitan police panel of pathologists offered contracts in 2004. The following year other complaints were presented to the GMC. After 2006 it was a prerequisite to qualify for the Home Office register that the practitioner be part of a group practice of pathologists. Patel concealed the fact that he was not part of a group from the National Policing Improvement Agency.

Somewhere along the line someone is not applying strict scrutiny. A pathologist told BBC News on 23 August that it was well known among some of the profession that Patel had been routinely giving the cause of death as natural causes when this cannot have been the case. Other cases dating back to 2002 have surfaced which saw three- and four-month suspensions for Patel in 2010 and 2011, one of which concerned dishonestly omitting key findings in relation to a murder victim. I trust there will be a thorough review of all cases he has handled over the last decade.

The coroner has explained his appointment of Patel in the first place on the basis that the only requirement under the coronial regime was that the person was a registered medical practitioner. These systemic deficiencies are unacceptable and jeopardise the search for truth. For Tomlinson's family it meant a prolonged and painful struggle to undo the damage done. There was delay while other pathologists were engaged who ultimately came to a different and unanimous conclusion that the death resulted from injury to the liver which caused internal bleeding and finally cardiac arrest.

But with conflicting medical opinion, the director of public prosecutions was unwilling to mount a prosecution against the police officer concerned. An inquest followed and the jury declared that Tomlinson had been unlawfully killed. More delay ensued while the decision to prosecute was reconsidered and a prosecution for manslaughter instigated. This cannot have been straightforward in the light of Patel's original opinion, one which he was unwilling to change.

Alongside this unfolding saga is an equally unpalatable tale of systemic fault within the police. Initially a statement of denial and non-involvement was issued. The City of London police also withheld details of Tomlinson's injuries from his family. When the police account was contradicted by the pictures recorded by a tourist, it was claimed Tomlinson was pushed out of the way for his own safety and later rumours were peddled that some protesters dressed up as police might be responsible.

The trial this year of PC Simon Harwood was successfully defended on the basis that he had only used reasonable force when he struck Tomlinson on the leg and pushed him to the ground. What the jury was unaware of was the background of this officer. In 2001 he had quit the Met on health grounds just prior to a disciplinary hearing. He subsequently rejoined the Surrey police and re-entered the Met in 2005. There were a series of allegations being investigated involving suspects being threatened, throttled, punched, and kneed, one of which was upheld.

By the time of the G20 protest Harwood was a member of the so-called elite TSG squad. The Independent Police Complaints Commission regarded this re-employment as "simply staggering". They recommended an internal investigation in public which is to be held on 17 September. They also revealed that the statements of three police witnesses who had seen an assault on Tomlinson with a baton had not originally been disclosed by police to the IPCC investigators charged with the duty of looking into allegations of deaths occurring at the hands of the police. On the same day as Tomlinson's death, Harwood had already had altercations with protestors and bystanders as well as pushing a BBC cameraman to the ground.

It could be regarded as the understatement of the century to wonder where quality control of evidential sources has gone. This has immediate ramifications for the overall integrity of our system of justice and should ring alarm bells in all quarters. The whole sullied picture is exacerbated by the iniquitous cuts in public funding which have already hit forensic science resources but are also impacting upon the quality and numbers of personnel who are willing to engage in the system at all levels.

If market forces are to be the determinative factor in the quest for truth then, just like most economies, we will be heading for irretrievable meltdown. Justice is not a business enterprise, still less a commodity. It is "truth in action".