Assuming that your case goes to trial, witness statements will have been taken and exchanged with the other party beforehand. If you have given a witness statement, it will usually stand as your 'evidence in chief'. This means that you will not normally be able to expand on the content of your statement without the judge's permission. You will be cross-examined on the content of this statement by the other party's representative.
At court hearings other than trials (for example, a hearing for summary judgment), evidence is normally given by witness statement only.
Even if you are reluctant to give evidence, one of the other parties could obtain a witness summons from the court, compelling you to do so. If you then fail to attend the trial to give evidence, committal proceedings (ie proceedings committing you to prison) could be taken against you.
