You may have been asked to be a witness because you have been a victim of crime, have seen, heard or know something in connection with a crime or have information about someone accused of a crime.
Special arrangements can sometimes be made for elderly, disabled or vulnerable witnesses.
You can contact the procurator fiscal who called you to give evidence if you have any questions, concerns or special requirements.
An expert witness is someone who is asked to collaborate in the process when specialised technical, scientific or artistic knowledge is necessary to understand or assess the evidence.
For example, it may be necessary to have a doctor explaining the wounds suffered by the victim and how they were inflicted, or a psychologist or psychiatrist describing the psychological characteristics of the accused so that his/her personality can be assessed, or a computer engineer showing how a piece of software was used to commit the crime.
In these cases, the doctor, the psychologist or the computer engineer use their technical and scientific knowledge to help understanding better what happened.