The programme, which stars Jennifer Saunders and Call The Midwife's Bryony Hannah, centres around the supposedly false imprisonment of Horgan's character Helen Stephens for the murder of her employer.
Speaking to journalists including Digital Spy, the pair explained that they intended for Dead Boss to be "silly" despite its dark premise.
"We watched a lot of high school films like Mean Girls," Walsh admitted. "We sort of liked the idea of writing the prison like a high school with the cliques and the bitchy remarks. There were stupid girls and sporty girls and whatnot.
"We don't want to write a social commentary on prisons at all. Ours is very much in the tradition of the old prison comedies.
"We didn't want to recreate prison life in comedy. We watched a lot of prison documentaries as well which nearly put us off writing it because it was so hardcore."
Horgan added that the murder mystery running throughout the series is intended to serve as a release from the confines of the Dead Boss prison.
"I was really glad that we had the murder mystery thing because I find now when I'm watching it I love getting out of the prison and getting involved in that other kind of life as well," she said. "I think if it were just set in a prison it would have felt a lot more sitcom-ey."
Asked if viewers will eventually discover the identity of the murderer, the Pulling creator teased: "You get led down a few alleys.
"The idea was that someone might think they've figured it out but then the next week go, 'Oh, well no she obviously did it'. And at some point you hope that [viewers will] think Helen did it."
Walsh continued: "Basically they're all dodgy, they're all seriously dodgy. There's not one person in it who's not a suspect."
Dead Boss begins tomorrow (June 14) at 10.30pm on BBC Three.