It is against the law to drive a car on a public roadway with "any detectable amount of a restricted controlled substance" in your system. This means that if the blood test reveals that there was any amount of THC, you are technically in violation of the law. However, if you had not smoked any marijuana that day, you may not have any THC left in your system. You should hire a lawyer because you do not want to be convicted of this, even if it is a first offense. If it were to happen again within then years, you could go to jail for up to six months. A lawyer may be able to discover defenses to the charge that are not apparent to you as a layperson.
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there is also a good possibility that you will be criminally charged for the THC, so you should at least talk to an attorney.
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