The manslaughter charge does not relate to the New Zealand victim.
Justice O’Hara told the Belfast Crown Court that it would be a “very complex sentencing exercise” and called for a “a comprehensive list of all the offences compiled person-by-person”.
McCartney first appeared in late July 2019 and has since been on remand in a Northern Irish prison.
McCartney’s vile abuse was discovered after a 2018 report to police in Scotland that a girl was being blackmailed on social media platform Snapchat.
A police probe tracked the blackmail threats to McCartney and a subsequent search of his home found thousands of images of young girls in “various states of dress and undress, performing various sexual acts”.
A lawyer for the prosecution at an earlier appearance said McCartney’s modus operandi was to “blackmail young victims into abuse” by threatening to post photos online before trying to get their younger siblings or cousins involved, BBC News reported.
Susie Hargreaves, chief executive of the UK’s Internet Watch Foundation, told the Metro newspaper: “The online coercion and abuse of children costs lives.
“Children who are blackmailed by these selfish, cowardly abusers are dying, and it is real.
“These children’s lives are torn apart by the cruelty of abusers who extort them for their own vile purposes.”
