I am not keen to get involved in this debate but...
The offence I assume he was arrested for was under s.9 Sexual Offences Act 2003 which reads as below
"A person aged 18 or over (A) commits an offence if–
(a) he intentionally touches another person (B),
(b) the touching is sexual, and
(c) either–
(i) B is under 16 and A does not reasonably believe that B is 16 or over, or
(ii) B is under 13.
(2) A person guilty of an offence under this section, if the touching involved–
(a) penetration of B's anus or vagina with a part of A's body or anything else,
(b) penetration of B's mouth with A's penis"
Johnson has a statutory defence that he genuinely believed the girl in question to be over 16.
Given that he has been bailed the police must need to carry out further enquiries or wait for some test results (it must be likely that he has been required to give a DNA sample - again this has not been disclosed in the media so far as I can see)
That defence might be easier to run successfully if he met her in a bar and she was looking over 16 (as many posters suggest) than if he picked her up from a school bus stop (there is nothing I have seen in the media to suggest one or the other)...
Whether he is guilty or not, as a matter of law time will tell - that is what the justice system (for all its flaws - and it has many) is for.
Isn`t the truth of the matter though that he is a 27 year old bloke and simply ought to know better; the fact that he is at least 12 years her senior is significant when she is 15/16 (in my opinion anyway). The situation is made worse when you recognise that he is (on any basis) incredibly wealthy and a role model for many.
It seems to me that if he avoids a prosecution or a conviction on the basis of the statutory defence (i.e. she looked old enough) then that might mean in law he should be acquitted; whether that means he is "innocent" I am far from certain. If, in a few years time when my daughter is 15/16 and going out she gets taken to bed by a 27 year old bloke I would string the bastard up.
If Johnson is not prosecuted or is acquitted because this is a set up or a case of mistaken identity then he has my sympathy - for now any sympathy I have rests with the girl. If the police did not think that the allegation was credible they would not have arrested him, if there was an easy answer I guess he would not have been in custody from about 9.00am until he was released at about 10.00pm last night.
I sympathise with the club - I don`t see what else it can do other than suspend him for now - do I want him playing for my team - NO, not unless he can demonstrate that this is some sort of a set up or mistaken identity.