There would also be the introduction of a "supporter" for each witness, who can sit near to a young person when they are giving evidence but not speak to them.

This person should be someone trusted and able to offer reassurance to the witness should they need it.

Mr Wallace said: "This policy will make sure that child witnesses should know in advance what will be expected of them, and where and how they will give their evidence to the court.

"Currently if a child turns 16 before a trial starts they are treated as an adult witness and lose their eligibility to any special treatment by the court. We will change this.

Jim Wallace: New category for witnesses

"Our proposals will mean that if a child is under 16 at the start of criminal proceedings they will be entitled to use a special measure when giving evidence even if they are over 16 when the trial starts."

Special measures would be relevant to people with a mental disorder which affects their ability to give evidence.

Mr Wallace added: "A new category of vulnerable witnesses should be introduced, flexible enough to cover any witness where fear, distress or intimidation could prevent them from giving their best evidence to the court in the normal way.