Watching underage pornography is a strict liability crime. No matter what the viewer thought the age of the child may have been, the reality is that she/he was still underage, and therefore, the crime was committed. Whether or not a doctor's opinion was given regarding the child's age or necessity of watching such a film is irrelevant to the guilt of watching the film in the first place.
In addition, the people who were responsible for making and releasing the film should be arrested as well. Whether or not the woman gave consent is her business, but the release of sexual videos that involve minors should be explicitly illegal in the United States. It feeds rape culture, and is has a detrimental effect on young women in society.
Read first. It saves you from looking like an idiot. It clearly states in the article that the actress was 19 years old at the time of the filming. The man was arrested because a doctor who didn't know that thought she looked underage. The article doesn't say what became of the case, so my suspicion is that after the actress testified he was acquitted.
No, the man in Puerto Rico should not have been arrested for watching a porn film that featured an underage actress. The man did not make or distribute the film. Even though buying or downloading the film may be a crime, the act of simply watching the film should be simply immoral.
While this is a very tough case and subject, I feel that proof is paramount to justice. I don't know the doctor, don't know his record or specialty or state of mind. There are certainly legal-aged women who look surprisingly young for their age, just as there are younger girls who look much older. Without validation of the girl's age, it's hard for me to justify charging someone for that crime.