There are similar concepts in American law.

Some crimes, (it used to be almost all crimes, now it's very few) require a particular state of mind, or mens rea. Mens rea, or "guilty mind", is a classic precept that goes all the way back to Roman law, and would have been considered an ordinary requirement for all criminal laws at the time the Constitution was written.

Unfortunately, the Constitution was silent on the issue of mens rea, and the Supreme Court refused to create a universal mens rea requirement for all criminal cases under the due process clause. As a result, there are now a great deal of "strict liability" crimes, which don't require any ill intent on the part of the accused at all. For example, a car accident in some states, even absent negligence, can be grounds for felony charges.

Prosecutors moved for this shift during the 70s-90s, since state of mind is so difficult to prove in court. In doing so, they overturned a precedent that goes back literally two millennia. What nobody realized was that mens rea was there for a reason, that it was difficult to prove by design. As a result we see lots of prosecutions for strict liability crimes that leave the defendant at a distinct disadvantage.

The second defense that comes up in this context is vagueness. Since penal laws must be strictly construed in favor of the defendant, i.e. any ambiguity in interpretation open in the statute must be resolved in favor of the defendant, vague laws can be and are struck down as being void for vagueness.

The theory here is not that the defendant did not bother to learn the law, it is that even if he had, the text of the law was insufficiently clear to give adequate notice to the defendant that his actions were illegal.

The real problem here, however, has nothing to do with the mens rea requirement. The real problem is that we have de facto dispensed with the presumption of innocence. In today's justice system, it is not a conviction that ruins a person's life, it is the decision to merely to bring a charge.

At the moment a felony charge is filed, before any determination of guilt has been made, the defendant may be incarcerated, for as long as nine years in some jurisdictions without violating the speedy trial requirement. All of his assets may be seized, before they have been proved to be involved in a crime of any kind. He will almost certainly be expelled from educational programs, usually with little or no due process, and lose his employment.

All of this happens before any proof has been shown, any arguments have been heard, any witnesses have been questioned, any evidence has been challenged, and before the defendant has had the chance to utter any words other than "not guilty." The fact is, in today's American justice system, your life is effectively over at the mere pointing of a finger.

The checks that were supposed to be the last line of defense, probable cause hearings before neutral magistrates and Grand Juries, similarly failed. Local magistrates often work hand-in-glove with the police, often in the same building, and since the probable cause standard is so low there is little obstacle to charging anyone for anything.

In states that use Grand Juries, jurors often meet repeatedly with the same prosecutors, month after month. The prosecutor is the only one that can call witnesses, present evidence, make argument, and even testify. He can refuse to present exculpatory evidence and witnesses, and the defendant is not even present to respond. From this fact comes the common saying among prosecutors, "I could indict a ham sandwich for the murder of a pig."

Most citizens are comforted by the notion, that no matter the unfairness in the initial process, eventually they will be able to present their case to a jury of their peers. However, even juries are no longer a right in most trials. Since the federal constitution's jury trial requirement was never incorporated against the states, most local magistrates are given the power to sentence defendants for up to six months in jail per count. Because most defendants face multiple charges stemming from the same conduct, there are countless American citizens spending years in jail, never having had their case heard by a jury.

We've given prosecutors the unbridled power to destroy anyone by signing a piece of paper.

Our justice system is just barely hanging on. Our rights still exist, but it's becoming impossible for an average citizen to effectively assert them. It's an interesting case to me. The decline of the legal system will be slow, and it's still far preferable to virtually any other system I've studied in detail, but it's scary to see it starting to happen.

The system still functions well, in some areas, especially for the rich. But the new unchecked system, (advocates would call it "streamlined"), pioneered upon inner city black and hispanic minorities is gradually moving up-market. Remember when you think about policies that seem to only apply to others, like loosening criminal law requirements, sovereign immunity, rampant disregard for the warrant requirement in poor neighborhoods, vehicle checkpoints, and stop-and-frisk: once the precedents are set, there is nothing to keep the government from applying them to you.