The Police Investigations and Review Commissioner (PIRC) is investigating the police response to a 999 call from an injured man in Penicuik.
A spokesperson for the PIRC's investigation team said: "We are investigating the police response following a 36 year old man's 999 call for assistance after he had been attacked and received serious injuries.
"The man made a subsequent 999 call and was attacked again before officers arrived.
"The investigation will focus on the call handling, management and control of Police Scotland's response to the incident on 3 September 2018 in Penicuik and the failure to refer the matter to the PIRC at that time."
The matter was referred to the PIRC by Police Scotland on 24 December 2018 following concerns raised by Lord Mulholland at the subsequent trial.
A report will be submitted to them in due course.