Sean 'Diddy' Combs' defense will cross-examine his ex-girlfriend and main accuser Cassie Ventura as he faces trial for sex-trafficking and racketeering in New York.

The music mogul kept a poker face this week as a pregnant Cassie described being physically and emotionally abused throughout their 10-year relationship.

In humiliating detail, she recounted a turbulent relationship with Combs that she said was consumed by violence and his obsession with a form of voyeurism where 'he was controlling the whole situation.'

That included directing her encounters with male sex workers right down to the copious amounts of baby oil she applied to maintain the 'glistening' look he desired - as many as 10 large bottles a session.

Combs' defense says he is guilty of domestic violence, but not of sex-trafficking or racketeering, and that the government is targeting him for his sexual preferences.