A trim does not count. Sam has to noticably cut or otherwise change the poofy hair before serving time.
This market closes when SBF is transported to his new home after sentencing. In the bizarre scenario where he isn't sentenced to a gazillion years in prison, this resolves by whether he has cut his hair by the original date of sentencing.
Since it is hard to set an objective line between a trim and considerable change, this will come down to a judgement call on my part. As such I will not be participating in this market to maintain impartiality.