Who's who in the Micheal John Duffy case

Long history of drug abuse

- Meets Evans and Duffy on May 8 and has threesome with them that night

- Invites them to parents' rural property in Picton the next day

- Killed either late May 9 or in the early hours of May 10, 2012

- Reported missing on May 25 by parents

- Decomposed body was found in shallow grave on May 31 at property

MICHEAL JOHN DUFFY, 34

- Former lover of Rachael Evans

- Admits to digging the shallow grave and burying Ms Ayers

- Denied murdering Ms Ayers saying he got caught up in Evans' twisted desire to kill

- Says he was having sex with Ms Ayers at her parents' property when Evans burst in and started strangling her

- Claims the teenager hit Ms Ayers over the head with a glass bottle

RACHAEL EVANS, 25

- Duffy's former lover

- Says she was on a cocktail of drugs in lead-up to murder

- Met Ms Ayers at a Campbelltown pub on May 8 and introduced her to Duffy

- Pleaded guilty to murder

- Received discount on sentence of at least 18 years and nine months for giving evidence against Duffy

- Says Duffy helped her strangle Ms Ayers

- Says she took Ms Ayers' body into the shower after the killing to get rid of Duffy's DNA

- Allegedly boasted about wanting to be a serial killer and about sending letters to Ivan Milat in prison

- Diagnosed with borderline personality disorder, paraphilia or sadomachism and substance abuse disorder

SCOTT DERBRIDGE, 24

- Pleaded guilty to being an accessory after the fact for helping to bury Ms Ayers' body

- Received a discount on sentence for giving evidence against Duffy and Evans

- Derbridge said he was "stunned" when Duffy told him "he broke Colleen's neck"

UNNAMED TEENAGER, NOW 18

- Granted indemnity as she was 16 at time of killing

- Denies hitting Ms Ayers with a glass bottle

- Says she was bullied into filming them having a threesome at Picton hotel room on May 8

- Says Evans "lost the plot" the next day when she heard Duffy and Ms Ayers having sex and said, "I'm going to do it"