In the early part of 19th century, the 'victim' of a crime had to pursue any prosecution individually, find their own witnesses and produce them before a magistrate, to be 'bound' to appear in court. Similarly, defendants also had to make their own arrangement to find people who would speak for them in court.
By the 19th century, the defendant was able to cross-examine prosecution witnesses and call their own witnesses but, unlike prosecutors, they could not compel witnesses to attend. Since trials were not scheduled, they did not know when witnesses would need to be in court, so organising this was difficult.
Witnesses who would testify to the defendant's good character were especially helpful, since even if the defendant was found guilty, evidence of good character might lead to a lesser punishment.
In the early part of the 19th century, the prosecution was often carried out by the victim of the crime and the witnesses gave their sworn statements to the court. By the mid 19th century, the use of prosecution Lawyers was becoming more common.
From 1879, when the post of the Director of Public Prosecutions (D.P.P.) was created, the government and the improving professional Police Forces started to act together in crime detection and prosecution. From this time, the state provided the witnesses for the prosecution.
Expert witnesses were called to provide specialist knowledge. Their use dates back to the 14th century. From this time people, such as surgeons, were sometimes called to advise on medical matters, first by the courts and later by the prosecution or defence themselves.
With the explosion of scientific knowledge in the 19th century, chemists, microscopists, geologists, engineers, mechanists and the like joined the ranks of the expert witness.
However, by the mid 19th century, there was concern within the judiciary that many of the expert witnesses were not impartial. In the Victorian era, science was viewed as inherently objective and there was great suspicion when disagreements of opinion arose amongst scientists.
The judges felt such experts were not being objective but supporting the views of whoever paid them. For example, Chief Justice James Fitzjames Stephen, felt such disputed evidence was "attributable to their want of moral fibre rather than professional disagreement".
At the same time, the law itself was coming under pressure to be more 'scientific' through a rationalisation of its processes and procedures.