Is it sexual assault if an 18 year old had sexual intercourse with a 16 year old?

In HI, any individual who is 5 years older than the minor could potentially face criminal charges. First-degree sexual assault is any sexual act with another person under the age of 14. It is also considered first-degree sexual assault when an individual 5 years older than a 14-15 year old engages in sexual relations with the individual between the ages of 14-15.

Either way, under no circumstnce is a 16 year old and 18 year old having sexual relations illegal. Assuming of course that it is consensual.

Depending upon the circumstances sexual intercourse between an 18 year old adult and a 16 year old minor could be deemed a sexual battery, but typically the term would be "stautory rape". The reason is that minors under the law are deemed incapable of consenting to many things because they are under age.

Assault is a different matter. Assault is the reasonable belief that a harmful or offense touching to a particular person would happen. An example would be if a person stated in anger he was going to strike you and threw a punch but missed striking you. Had the thrown punch hit the victim, the striking would be called a "battery".