It would be logical for Kincaid to keep an eye on Brutis. You don't leave a penal legionnaire running around.
So We'll say Brutis is in a cell and in bureaucratic limbo, being neither in arrest nor released. Kincaid, knowing how things work and calling in a few favors, in kinda lending the kinda prisoner as a personal protection device, earning a few rude remarks and a few relieved looks along the way.
Brutis is a penal legionnaire, his life is forfeit to the emperor. He has deserted once. Normal penalty is being hunted down and be executed by any means possible along with anyone caught helping them. The exception is when there's a mass rout and the army regroups, counterattacks and is victorious, then the survivors are sent to penal legions as a sign of mercy. Another is desertion when mind-controlled by psykers. Then the survivors are mind-scrubbed and used as combat servitors. Imperial Guard. Not for the faint of heart.
Brutis cannot hide he's a penal legionnaire without going about dressed very suspiciously . He's got a barcode tattooed on his forehead along with the word PENAL LEGIONNAIRE. He's also wearing a collar with a little blinking green light. So he needs Kincaid to move about. The armor Kincaid wears is very recognizable. She walks about dressed in Adeptus Arbites combat armor, and is usually given wide berth. They are not the most subtle members of this operative cell.
The adeptus arbites fortress would also be a good place to meet Muggie's character if he/she wants to play an adept who is called in to examine the case. Being a noncombatant she could use a bodyguard so that's an excuse for Kincaid to use if questioned.
How does that sound?