Which can be dangerous.
Do any of us publicly admit to error? It is a brave person who does and to do so runs somewhat contrary to human nature, which is what it is. It is ingrained in each of us that when we think we are certain of something, we must be right, when it should actually be the other way round. We should remind ourselves that the more we think we are right, the more likely we are to be wrong - this has been demonstrated time and again in my own experience of watching others and thinking about my own actions in real situations.
In my trade, there is a useful saying: Measure twice, cut once. This is good to remember, not just for cutting and joining things. You can be certain you are right about something that seems very obvious and simple, but find you are completely wrong. Unfortunately, intelligent decisions require humility, which is a quality in short supply.
I believe in the past bodies like the police were covering things up for fear of the consequences and cutting corners or inventing evidence in the firm belief that they were dealing with a guilty person. This is a major example of the fallacy of certainty (or 'the fallacy of alleged certainty', as it is sometimes known formally). The policeman assumes guilt, thus everything he hears is interpreted through that prior conclusion, in a process of convergence bias. This is of course a very common intellectual flaw, and we all fall into it from time-to-time. It probably has an evolutionary origin in that it may have been necessary for primeval Man to think and analyse situations quickly for survival purposes, resulting in a tendency against balanced or convoluted thinking. There are a few more checks and balances in the system now, but I see no fundamental reason the same fallacy should not be widespread today, as I believe human nature is at play.
If anything, I believe it could be worse now. For one thing, there is the danger of deference to scientific evidence, such as DNA. Genetic identification is widely seen as infallible but it isn't, and it should not be a means for the prosecution to circumvent the burden of proof.
The jury is meant to be one of the checks in the system against wrongful convictions. Juries have always made bad decisions. The general flaw in the institution of juries is very obvious. It's argued that inquisitorial criminal justice systems have fewer miscarriages of justice, but I think it more likely that in systems without juries there is a greater readiness to overturn wrong decisions. The Anglo-American common law system of jurisprudence sanctifies the jury, which is really a way of entrenching wrong or fallacious decisions.
Yet a jury of very ordinary people that can hear and consider all the evidence and facts in the round provides a last resort against the natural tendency to believe experts uncritically or defer to voices of authority: a tendency that is especially prevalent among experts themselves. A panel of judges hearing a case will naturally tend to demote their own common-sense and everyday experiences and believe experts. A jury, by contrast, can decide in secret and is not accountable or answerable for its decisions, thus not subject to the ordinary social pressures and influences that can lead to uncritical acceptance of expertise; and the jury can, if it so chooses, disregard expertise and acquit a defendant by considering the evidence from a layperson's point-of-view and measuring it against everyday experience and the juries' own idiosyncratic evaluation of the experts - which will often be more accurate than that of the experts themselves. This protection has been eroded by majority verdicts, and a climate in society that gives overdue regard to credentials and 'science' and demotes experience and subjectivity. Unless jurors can think for themselves, they may be tempted just to ratify expert opinions. The Sally Clarke case seems to be an example of this.
On a different but related note, I have been involved in training in different places and have closely-observed how schools, colleges and universities now work. There is very much a belief that all must pass, with the result that many young people are carrying around useless paper credentials rather than gaining skills and experiences. Does this encourage the increasing spread of robotic deference to expertise and credentials that 'educated' people especially can sometimes fall into? Does it encourage needless abstract thinking that militates against practical sense and experience, making good decisions rarer to find?