Is it legal to send nude pictures of a minor to an adult?

There are two bodies of law that address your question. State law and Federal law. I cannot address what your state’s law says about the issue and it may well be more restrictive than Federal law. That said, there is a very strict Federal law governing transmission of pictures of people who are under 18 years of age. You say in your question that the depiction was not lascivious, but that is a subjective conclusion which might not be shared by a prosecutor making a charging decision. It is a Federal crime to take or send pictures containing “lascivious exhibition of the genitals or pubic area of any person” under the age of 18 (note that “lascivious exhibition” may have a different meaning than your conclusion that it’s not a lascivious photograph). I would also mention that pictures of clothed minors have been found to violate child pornography laws. On the other hand, it is possible that a nude photo of a minor in the right context would not be child pornography, but it’s hard to tell from the details you provided. I would urge a client of mine to refrain from taking or distributing any nude photos of anyone under 18. The foregoing is for general public informational purposes only. It does not create an attorney-client relationship.