Section 18 assault charge, yet he wasn't there?

[confusingstuff]

Hi and thanks for any advice in advance.

My son is in custody on remand and facing a section 18 assault charge, which is going to trial this week. however i am 100% certain he didnt do it as he was with me at the time!

Yet he has been arrested for it, there apparently was only the victim at the scene of the crime and no other witnesses.

This person has known my son for several years and named it as being him, and did a id parade and identified the person as my son as commiting the assault to him.

How does this stand in a court of law and trial? im standing as a witness to give my wereabouts and my sons on the relevant day

there are no other witnesses at all just the victim and the id parade

[New Judge]

Or was the other witness lying or perhaps mistaken?

[confusingstuff]

he was really in the house because i am really cautious due to my other younger son been kidnapped, we have a panic alarm installed too etc so i am 100% yet the jury found him guilty, even though it is a know fact around our area that the man who was prosecution witness/victim is a known alcholic and frequents the park nightly drinking cans of beer etc, i really am unsure what to do next, if i can do anything at all :( and wondering what the sentence will be for this