Mo. Rev. Stat. § 565.090: Harassment, first degree, penalty.

1. A person commits the offense of harassment in the first degree if he or she, without good cause, engages in any act with the purpose to cause emotional distress to another person, and such act does cause such person to suffer emotional distress.

2. The offense of harassment in the first degree is a class E felony, unless the defendant has previously been found guilty of a violation of this section or section 565.091, or any offense committed in another jurisdiction which, if committed in this state, would be chargeable or indictable as a violation of any offense listed in this section or section 565.091, in which case harassment in the first degree is a class D felony.

3. This section shall not apply to activities of federal, state, county, or municipal law enforcement officers conducting investigations of violation of federal, state, county, or municipal law.