So how is the having a sexual relationship okay, but a picture isn’t? Sec. 22.011 of the Texas Penal Code, which covers sexual assault, defines a child as “a person younger than 17 years of age.” But Section 43.26 says defines child pornography as “visual material that visually depicts a child younger than 18 years of age … engaging in sexual conduct.” Sexual conduct includes “lewd exhibition,” so a nude photo of a 17-year-old is illegal, even though having sex with them is not.
It’s unclear why there is a discrepancy between the age restrictions for these actions, but it could have to do with the evolution of who is considered a minor. A proposed draft of the penal law from 1970 defines a minor as someone under 16, a 1972 draft says under 17, and today, a minor is someone under 18. Laws against child pornography and related offenses seem to be in lock step with who is considered a minor, as those drafts show. Similar federal laws also define a child as a minor under the age of 18. Since the age of consent is different, that accounts for the one-year gap.