‘And the scribes and the Pharisees bring a woman taken in adultery, and having set her in the midst they say to him, “Teacher, this woman has been take in adultery in the very act”.'
‘The scribes and Pharisees' (significantly not a usual Johannine phrase. It is more Lucan) bring to Him a woman who has been caught in adultery, and deliberately stand her in the middle of the crowd in order to draw attention to her. It is being made quite clear that they wanted to trap Jesus and to make sure that the crowd were aware of His failure.
We must certainly immediately ask ourselves, where is the man, for he deserves similar punishment? It may, of course, be that he managed to escape from their clutches when they caught the pair, but it is certainly equally possible that they were not really interested in the man, and that he may even have been one of themselves. But to them he was irrelevant for he would not serve their purpose, which was not to promote righteousness but to show up Jesus.