Explaining a few key differences between the criminal courts in the U.K. (in particular England and Wales, Scotland and Northern Ireland have their own idiosyncrasies) and those in the U.S.
There is no constitution
The fundamentals are broadly similar: laws are set using the common or case law system, in which past court judgments are the interpreters for what is and is not legal. However, the British legal system is not built around a constitution, it’s driven by precedent and various acts of parliament, and some of these go all the way back to Magna Carta in 1215. Scottish law is slightly different, in that their laws are set both by common law and civil law (in which past precedents are abandoned in favor of fresh legislation). But in neither case is there a sole central document from which the law is derived.
Judges decide what goes to criminal court
Once someone has been arrested in the U.K., the Crown Prosecution Service (C.P.S.) takes their case before the Magistrate’s Court (in which three judges decide whether there is enough evidence to pursue the case through the courts, so there’s no grand jury). If there is enough evidence, a formal indictment is served, assuming the case is to be subjected to trial by jury (some minor cases remain a matter for the Magistrate’s Court). Speaking of which…
American juries are selected and agreed upon by counsellors for the defense and prosecution, and this can become a part of the drama of court (particularly in TV courtroom dramas), whereas in the English and Welsh system, the selection is random. Juries are selected from a list of eligible candidates—British residents who are aged between 18 and 70, basically—on the electoral roll. Jury duty can arrive at any time, and is expected to be honored where possible, although it can be deferred in extreme circumstances.
Solicitors and barristers
Then there’s the terminology: while technically everyone in a courtroom counts as a lawyer, there are two distinct disciplines at work in the English legal system and these have their own job titles: solicitors and barristers.
Solicitors work with clients on a broad spectrum of legal matters, offering advice, and drafting legal documents. They can represent their clients in court—albeit for minor cases—but are far more likely to be doing everything that happens outside of the court proceedings, because that’s their main area of responsibility. They’re the equivalent of special law practitioners, real estate attorneys, health care attorneys and so on.
Barristers are the courtroom experts, the litigators. They’re the people in the short wigs and robes who do the verbal fencing and cross-examinations in front of the jury. The solicitor will take their client to a barrister and ask them for courtroom representation, which allows the solicitor space to administrate the necessary documents and files needed for the trial.
The person in the long wig and more ornate red robes is the judge, and the purpose of all of these items of costumery—which are graduated subtly to denote status—is to create a respect for the court, and for the positions each person holds within the court. While civil court cases can be heard without the finery, a bewigged judge (or a Queen’s Counsel, senior barristers with shorter wigs) is not just a person making a decision, he or she is also a representative of the whole British legal system, and for criminal justice, the wigs (while clearly based on archaic modes of dress) do underline this point very well.
After that, the whole guilty as charged/not guilty thing is exactly the same, so everything else should be fairly easy to follow.