You're facing charges after failing a drug test, and you start wondering just how accurate those tests are. Can they really be trusted in such a serious case? How long do they work for, anyway?
It all depends what type of test was used. There are five main ones, each with their own useful time frames.
Saliva tests usually only work for a few hours. The longest they could produce accurate results is a couple of days after use.
Urine tests tend to work for the past seven days or so, depending on the drug in question. It is worth noting that some studies have produced results from usage in the previous 30 days or longer when it comes to marijuana.
Hair tests are less common, but they have a very long period of time during which they can produce results. They usually work for two to four months.
Sweat tests are also not used as frequently. The time frame for these tests is unclear, as subjects keep the patch on for a long time and simply wait to see if results are found. These tests also aren't usually trusted by experts since there's a very good chance that outside contaminants can ruin them, perhaps producing a false positive.
Typically, blood tests are considered the most accurate of the five kinds of tests. The window is also very small. They work for about 48 hours for most drugs.
Do you think your test fell outside of the acceptable window? For instance, maybe you were given a blood test a week after the alleged use, and now you're wondering if that those test results can be trusted at all. If so, be sure you know what legal options you have.
Source: CRC Health, "Drug Tests Accuracy," accessed Feb. 02, 2018