He also wanted to use the play to explore other themes and provide a reflection of New Zealand society, such as the media and race relations.
Those themes are conveyed in the character of Mau Vaiaga, a new Samoan migrant, who has been jailed for committing a crime out of ignorance - killing and eating a kakapo.
Mau Vaiaga, portrayed by the media and talkback hosts as the "worst criminal in New Zealand", shows the absurdity of the justice system as his sentence is longer than King's.
Natano Keni, who plays Vaiaga, describes his character as a quiet unassuming guy from the islands who just wants to work hard and start a new life but has made a mistake and is being punished for an act considered quite normal back home.
McCaskill says that Natano's character brings out the worst in New Zealand's underground racism with talkback radio fuelling it.
"Natano is a character who has done a minor crime and the New Zealand public get up in arms because he's an immigrant and he can't do that here," he says.
The prisoners' lawyer, Waimanea Huia, played by Kali Kopae, is an up-and-coming Maori lawyer who is only defending these two clients to raise her profile and further her career. Huia has to juggle career and obligations to her iwi who funded her through law school.
McCaskill focused on the authenticity of the characters in Manawa, especially Huia and Vaiaga, as a great deal of effort was made by the actors to make them as real as possible.
Kopae referred to her lawyer friends to check the language they spoke, but admits her character is just a little exaggerated for drama.
"I watched YouTube and talked to my lawyer friends as I want to show the air of
professionalism they have. But they say in real life they're a lot nicer," she says.
Keni, who grew up in a Samoan home in Wellington, mimicked the language, accent and mannerisms of his own father and grandfather. "My character speaks 'Freshlish' and my mum said I reminded her of my dad when she saw the play," he says.
McCaskill initially wrote the play for an audience who share his views on the justice system but based on feedback from some viewers, it has provided food for thought for people who differ. He says by giving the audience a "behind the scenes" look at a
criminal and based on his experiences with troubled youth, he knows that deep down there can be a good person beneath the hard shell.
"I wrote this originally to preach to the converted but it's provoking to people who think the opposite ... you see behind the camera the real person and I wanted to make these characters likeable."
He guarantees that by the end of the play the audience will see a good heart in all of the characters.
What: Manawa
Where and when: Basement Theatre, to November 3
