Hello I am a lawyer with over 15 years experience I will try to help you with this.
Have you signed a witness statement about this incident. When is the court date?
Where a witness is simply invited to attend Court, the witness is not at that stage under any legal requirement to attend. However if the Court believes that a witness is likely to be able to give significant evidence, but a summons will be necessary to compel that witness’s attendance, then a witness summons can be issued.
A witness who fails to attend court without just excuse despite service of a witness summons upon that person, is guilty of a contempt of court, and can be punished with imprisonment of up to 3 months. Forgetfulness is not usually regarded as a reasonable excuse.
If a Court believes that a person who has been served with a witness summons is unlikely to comply, the court may issue a warrant to bring that witness before the court. This will entail police arresting the witness and bringing that person to court. The court will then decide whether the witness will be kept in custody until the hearing, or whether the witness will be allowed bail (with or without conditions).
Have you expressed reluctance to the police? If so, then they should contact the CPS to decide what to do. If you haven’t done so then if you do not attend court attempts will be made to contact you. If you are a crucial witness in the case and aren’t at court the CPS will apply for an adjournment. Which may or may not be granted. If the case is adjourned the court may grant a witness summons at this point and if you do not respond to this then you can be arrested etc. as set out above.
If the case is in the magistrates court then there will be less enthusiastic attempts to get you to court than in the crown court.
Your choice really is whether to respond to the request to attend by letting them know you don’t want to go or to just not turn up and hope you don’t get summonsed. If you notify the police that you don’t want to attend it might be a good idea to write to the court as well and make sure you tell them you have informed the police. The reason for this is that if (as is likely) the CPS do not get round to applying for a witness summons in advance they will find it harder to get an adjournment if they were warned in advance. Also the court will view more favourably f you have been honest about not wanting to give evidence.
So, in short you ca be compelled to give evidence but there is a good chance it won’t happen.