A fourth man was arrested over the murder of "devoted stepdad" Stephen Maguire who was shot dead in his living room.
The 27-year-old was killed at his home on Guildford Road, in Birkdale, shortly before midnight on March 22.
A post-mortem examination confirmed he died as a result of a gunshot wound to the abdomen.
In May, officers arrested and charged three men in connection with the attack who later pleaded not guilty.
Now, detectives have confirmed that a fourth man was arrested on suspicion of murder.
The 34-year-old, from Liverpool, has been taken to a local police station for questioning.
Detective Chief Inspector Rachel Wilson said: “We have arrested a fourth man in connection with the murder of Stephen Maguire today, which is another positive step forward in seeking justice for Stephen and his family.
“Despite this arrest, an extensive investigation remains ongoing and we are still keen to speak to anyone with information on this brutal crime.
“Enquiries are still ongoing to trace a dark coloured Mercedes seen making off from the scene of the crime in the direction of New Cut Lane.
"If you saw, heard or captured any images of this vehicle, be it the smallest detail, please get in touch.”
Karl Corson, 27, of Columbine Close, Melling; Jack Higgins, 21, of Waresley Crescent, Fazakerley; and Ryan Smith, 21, of Colquitt Street, Liverpool city centre, are all charged with murder, two counts of kidnap, possession of a firearm, possession of ammunition and robbery.
According to the charges, they murdered Mr Maguire and robbed him of an orange KTM motorbike, a green Kawasaki motorbike and a red Honda motorbike, of a value unknown.
The men are accused of kidnapping a teenage boy and a 19-year-old man on the same date as the shooting, who were allegedly "unlawfully and by force or fraud took or carried away" against their will.
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The charges also allege that the defendants were in possession of a handgun and 9mm ammunition.
They have pleaded not guilty to all charges.
Anyone with information is asked to submit information via the UK Police Major Incident Public Reporting Site, at the following link: https://mipp.police.uk/operation/05MP20M36-PO1 where it will be treated sensitively.
You can also pass on information anonymously via the charity Crimestoppers on 0800 555 111 with reference 20000166174.