The matter regarding the electric meter man is mentioned in the European Convention of Human Rights :
Article 6-Fair Trial,where it states that the right to have witness examined had been denied of Jeremy when the prosecution had used PII ( a gagging order ) preventing statements for the defence,such as that of the visit of the electric meter reader who had witnessed one of Sheila's psychotic attacks hours prior to the murders.
Ewen Smith had taken a witness statement from the employee and had then found out that he'd made a statement to the original investigating officer,only for it not to be disclosed to Jeremy or his legal team and also not listed under PII rules.