Drugged driving is a topic that doesn't get as much publicity as drunk driving. DUIs are more common and they "grab the headlines" more so than drugged driving cases. This can lead to some misconceptions about drugged driving cases.
First, let's talk about drunk driving cases. When someone is charged with a DUI offense, there are usually pieces of evidence that can establish their intoxication. Blood tests and breath tests are the most notable of these types of evidence. The reason these tests are reliable and effective is because alcohol isn't in the blood stream for very long. Thus, when alcohol is detected in your blood, it is reliable evidence. It shows that you recently consumed alcohol as opposed to consuming it weeks ago and having it turn up in the test.
This is exactly why drugged driving cases can be so confusing. In many cases, the substance at the heart of the drugged driving case could have been in the person's system for weeks -- not because they recently consumed it, but because it lingers in the system for an extended period. THC in marijuana does this. It stays in your system for up to five weeks.
For this reason, drugged driving charges are very bizarre cases and there are legitimate reasons that a defendant may be falsely accused of driving under the influence of drugs. If you have been accused of drugged driving or are facing criminal penalties as a result of a supposed drugged driving incident, then you should consult with an attorney immediately.