How do you prove intent then? It certainly can’t just be based on the honesty of the alleged perpetrator, can it? Common sense and reason has to play into it, I would think.
I thought I addressed this above and is NOT based on the honesty of the alleged perpetrator. What ancillary data exists contemporaneous with the assault?
For example:
Did the assailant have an erection?
Did the assailant say anything that could be construed as sexual or inappropriate, either before, during or after the assault?
Did the assailant make any guttural/sexual noises before, during or after the assault?
Does the assailant have a history of other instances where a similar assault occurred with one of the above modifiers?
Was the assailant in possession of pornography that would support the idea that this assault was sexually motivated?
Has the assailant ever communicated (perhaps via social media?) their desire to commit such a crime, or that such physical contact is a sexual desire for them?
If yes to any of the above, that points towards that contact being sexual in nature and is up to the jury to decide.
The lack of any of the above does not preclude it from being sexual, but in the absence of evidence, it would be more difficult to prove.
Again, I have no idea if the "shower incident" was sexually motivated or not. I do strongly disagree with your assertion that it must have been because they were naked, alone and in a shower.