Tampering with evidence is illegal under both federal and state law. The crime involves altering, destroying, or concealing physical evidence with the intent to affect the outcome of a criminal investigation or court proceeding.
Remember that scene in "Up In Smoke" where Cheech gulps down the joint he's smoking in Chong's car when he hears the police siren behind them? Very funny scene but the two stoners may not have known that Cheech committed two crimes. Possession of any amount of marijuana in Los Angeles in 1978 was illegal, so that's the first one. And, by swallowing the "evidence" of the first crime, Cheech committed a second crime—tampering with evidence.
Tampering with witnesses is also a crime. For more information about witness tampering, see Intimidating a Witness.
A person commits the federal crime of tampering with evidence when he or she knowingly alters, conceals, falsifies, or destroys any record, document, or tangible object with the intent to interfere with an investigation, possible investigation, or other proceedings by the federal government. (18 U.S.C. § 1519.) State laws also make it a crime to tamper with evidence in officials proceeding and investigations.
When a person intentionally destroys a document or item that is not, and will not, become evidence in an investigation or other proceeding, there is no tampering with evidence. If Cheech had been smoking a clove cigarette that he thought was a joint of marijuana (a mistake Cheech would never make) and swallowed it when a cop pulled the car over for speeding, he would not have tampered with evidence. Even though he believed he was smoking a joint and intended to destroy evidence of that, his belief does not change the fact that there is no evidence of a crime.
In order to convict a person of tampering with evidence, a prosecutor must prove that the person knew that the item with which she allegedly tampered was evidence (or could be evidence) in an ongoing or future investigation or proceeding. For example, if a janitor feeds a stack of documents into the shredder, she probably has not knowingly tampered with evidence, even if the stack included a document that showed the business for which she worked was a money-laundering operation for a criminal syndicate. However, if the boss shredded that same document, it is far more likely that he knew he was destroying evidence.
A prosecutor must also prove that the individual charged with tampering with evidence intended to interfere with an investigation or other governmental proceeding when he altered or destroyed the evidence. So, a person who inadvertently or accidentally alters or destroys a document or thing that he knows to be incriminating probably has not tampered with evidence. If the syndicate boss unintentionally knocks over a cappuccino onto incriminating accounting records, making them illegible, he has not knowingly altered the evidence (although he may not be sincerely sorry for his clumsiness).
A person who destroys evidence out of fear of an investigatio or before a crime has been committed, intending to hide a later crime, has tampered with evidence. For example, the man who gets his wife drunk before leading her to the pool to kill her in a staged accident, but stops on the way to the diving board to wipe clean her lipstick from the whiskey glass, has tampered with evidence (in addition to committing murder). And, the inside stock trader who deletes emails to his source in order to leave no trail of illegal stock tips has destroyed evidence even though he is not under investigation at the time. (He is also guilty of being incredibly naïve if he thinks a deleted email can't be found!)
As with most crimes, there are several defenses that a person charged with tampering with evidence may raise. Here are a few of them.
An individual who can show that she lacked knowledge that a damaged or destroyed piece of evidence was, in fact, evidence will be acquitted. If the janitor in the example above can show that she only worked at night, had no contact with the people in the offices she cleaned, did not know what business they were in, and had no information about their illegal activities, she can avoid a conviction.
Even one who destroys or alters a piece of evidence but who did not intend to interfere with a governmental investigation or proceeding has not tampered with evidence. If Cheech had finished that joint in the normal way before he heard the police siren, he could not be charged with tampering with evidence. While it is true that he would have destroyed evidence of drug possession and use, his intention was to get high, not to hide the joint.
The U.S. government takes tampering with evidence very seriously. A person who is convicted of the crime under federal law may face a prison sentence of not more than 20 years, a fine, or both. (18 U.S.C. § 1519.)
State penalties vary. Some states make any tampering with evidence a felony offense. Other states make it a felony to tamper with a felony investigation or case and a misdemeanor to tamper with less serious cases. You'll need to check your state laws for the applicable penalty.
As that potential penalty indicates, tampering with evidence is a serious charge and can arise in many situations. As with all serious legal problems, be sure to consult a lawyer experienced in criminal law if you have questions regarding a crime or investigation.