A man who allegedly killed Labor identity Tim Picton in Perth has admitted assaulting another man days earlier.

Mr Picton, whose brother is South Australian minister Chris Picton, died after falling and hitting his head in an alleged assault in Northbridge in December.

Brodie Jake Dewar, 20, has been charged with manslaughter over that incident.

Brodie Dewar leaves court surrounded by reporters holding microphones.

Brodie Dewar pleaded guilty to assault causing bodily harm over the Kalamunda assault.  (ABC News: David Weber)

He was also charged with act or omission causing bodily harm in relation to an incident in Kalamunda in the early hours of Christmas Day.

Appearing in Armadale Magistrates Court on Wednesday, Dewar pleaded guilty to the lesser charge of assault causing bodily harm.

Perth Magistrates Court had heard in February that Dewar had knocked a man unconscious outside the Kalamunda Hotel shortly after midnight. 

An older pub building in a suburban street

The incident happened outside the Kalamunda Hotel. (ABC News: David Weber)

The court was told Dewar had recorded the unconscious victim on his mobile phone, saying “don’t hit on my sister”.

He had called people over to help the victim, who later told police he had no memory of the attack, the court heard.

The 20-year-old is expected to appear in Armadale Court for sentencing on May 6.

Dewar is scheduled to appear in the Stirling Gardens Magistrates Court on April 29 on the manslaughter charge relating to Mr Picton’s death.