Thank you for your question.
In Indiana, this would actually be charged as "Contributing to the delinquincy of a minor", and could be either a Class A Misdemeanor or Class C felony if the person giving the alcohol to the child was at least 21 years old.
The relevant statute reads in part:
Contributing to the delinquency of a minor
Sec. 8. (a) A person at least eighteen (18) years of age who knowingly or intentionally encourages, aids, induces, or causes a person less than eighteen (18) years of age to commit an act of delinquency (as defined by IC 31-37-1 or IC 31-37-2) commits contributing to delinquency, a Class A misdemeanor.
However, the offense described in subsection (a) is a Class C felony: if:
(A) the person committing the offense is at least twenty-one (21) years of age and knowingly or intentionally furnishes:
(i) an alcoholic beverage to a person less than eighteen (18) years of age in violation of IC 7.1-5-7-8 when the person committing the offense knew or reasonably should have known that the person furnished the alcoholic beverage was less than eighteen (18) years of age;
All a prosecutor would need to establish therefore is that a person knowingly or intentionally gave alcohol to a minor to sustain a conviction. All the police would need to actually charge or arrest someone is a reasonable, good faith belief that a crime has been committed.