Graham Dwyer's murder trial has heard he allegedly sent Elaine O'Hara text messages days before her disappearance telling her he was going to stab her outdoors in a remote place.

The architect from Kerrymount Close, Foxrock denies murdering the childcare worker at Killakee mountain in what's alleged to have been a sexually motivated attack.

'If anything happened to you, who knows about me?'' a text message the prosecution claims Graham Dwyer sent to Elaine O'Hara 6 days before he allegedly murdered her.

The jury is hearing details of texts allegedly sent between two phones later found in Vartry Reservoir that have been dubbed the master and slave phones.

The prosecution claims that the couple used them as part of a BDSM relationship that involved stabbing.

The master tells the slave to keep August 22nd free – that's the day Elaine O'Hara went missing.

He warns her that as punishment she's getting knifed in the guts ...while bound to a tree deep in the forest in what another text describes as 'a really remote place' where  'no one will find us'

She replies 'now, I'm terrified'. On the day texts from the master phone direct her to park at Shanganagh cemetary – where the childcare worker was last seen by a jogger just before 6pm.

The master says she'll be back at her car by 8pm that evening. 

Earlier, Graham Dwyer's murder trial has heard text messages in which he allegedly agreed to impregnate Elaine O'Hara (36) as a reward if she helped him stab a girl to death.

The architect of Kerrymount Close in Foxrock denies murdering the childcare worker at Killakee mountain in Dublin in August 2012.

The jury is hearing further details of the almost daily contact by text message between Ms O'Hara's iPhone and a prepaid phone.

The prosecution claims this phone was used by Mr Dwyer as part of their BDSM relationship.

In July 2011, the man says he will punish her by raping her and leaving either deep stab wounds, or marks on her neck.

She texts 'please sir I don't want you to stab me anymore, I'm scared you're going to kill me''.

He replies 'you won't die, night night'.

The jury heard the man also agreed in these texts to get Ms O'Hara pregnant using the words 'a life for a life, help me take one and I'll give you one' - before outlining plans to rape and stab an estate agent in an empty house in Cabinteely.