Today, much of our current criminal law is derived from the common law, at least in relation to its broad features. Substantive and procedural criminal law under the common law was different from that practiced in continental Europe, where investigation and criminal law enforcement was conducted mostly in private (with use of the "rack"), having private trials and private punishments. Common law criminal procedure was different, with public trials and public imposition of punishment.
But, today's criminal procedures and punishments differ in many respects from that under the common law. Currently, a criminal defendant can appear in a modern American court and refuse to enter a plea to criminal charges, which results in the court entering a plea of not guilty. But at the common law, matters were different, the purpose being to force a plea. If a defendant refused to enter a plea under common law procedures, he was carried back to prison where he was forced onto the ground, and heavy metal objects were placed on his body in a process named "pressing". This was done in an effort to force a plea, but many unfortunate defendants were "pressed to death."
Lots of the substantive common law crimes were judicially developed over centuries without legislative enactments. However, those were not the only crimes that could be prosecuted and punished in Medieval England because Parliament could enact laws creating crimes that applied "ex post facto". This allowed for punishment of conduct that was legal at the time of commission.
At common law, a party who had an interest in a case could not testify. This applied to both civil and criminal cases, and consequently, criminal defendants could not testify at their own trials. Changing this rule by legislation started in the latter half of the 19th century, but was not completely ended until the 1960s.
Under the common law, punishments for criminal convictions were different from what we have today. In addition to fines and imprisonment, minor offenses could be punished via the pillory, but felonies were punished via more gruesome methods: besides imprisonment, cutting off of ears or other body parts, disemboweling, hanging, being drawn and quartered (pulling off the limbs of the body), and beheading were common punishments. In the movie, Braveheart, there was a depiction of William Wallace's execution; first, he was disembowelled, then beheaded. Today, we consider such punishments as being "cruel and unusual".
If a defendant was convicted of a crime, there was no process for appeal and punishment swiftly followed the verdict. Two cases provide examples of that swiftness, and attached are a few pages from historical records of Henry VIII's reign. The first page reflects the arraignment, trial, verdict and punishment for the Duke of Suffolk for a conviction. The 2nd and 3rd pages concern the end of Sir Thomas More's trial, his conviction and sentence. His "crime" was denying that Henry VIII, having established the Church of England, was the supreme authority over the church, a charge we would consider today as completely political. This clash between More and Henry VIII was premised on the fact that More was Catholic and Henry was at war with the Pope. More was beheaded within a week after the verdict in his case. See this for more information.
Today, we would consider common law criminal procedures crude and repulsive, but so did our Founding Fathers. Lots of the first 8 amendments to the US Constitution address these then existing common law procedures and banished them. In short, these amendments are in sharp derogation of the common law: they are anti-common law.