The brother of a former News of the World showbusiness reporter who died after speaking out about phone hacking is to give evidence to the Leveson Inquiry.
Sean Hoare, 48, claimed his ex-editor Andy Coulson was "well aware" of the practice of illegal voicemail interception at the paper, something Mr Coulson strongly denies.
Mr Hoare, who suffered from alcoholic liver disease, was found dead at his home in Watford, Hertfordshire, in July after he started drinking again to cope with the stress of the attention on him as a phone hacking whistleblower, his inquest heard last month.
His brother Stuart is expected to speak about the strain the journalist faced while working at the News of the World.
The inquiry into press standards will also hear evidence from Independent on Sunday deputy editor James Hanning and former News of the World sports reporter Matt Driscoll, who made a successful employment tribunal claim for disability discrimination after he was sacked by the paper.
Tuseday's witnesses include Piers Morgan, the former Daily Mirror and News of the World editor-turned CNN interviewer, who will appear via videolink from the United States.
Prime Minister David Cameron set up the Leveson Inquiry in July in response to revelations that the News of the World commissioned a private detective to hack murdered schoolgirl Milly Dowler's phone after she disappeared in 2002.
The first part of the inquiry, sitting at the Royal Courts of Justice in London, is looking at the culture, practices and ethics of the press in general and is due to produce a report by next September.
The second part, examining the extent of unlawful activities by journalists, will not begin until detectives have completed their investigation into alleged phone hacking and corrupt payments to police, and any prosecutions have been concluded.