If detective Sims was so certain Lacey was involved with the escapees, why didn't he have even a single cop following Lacey or watching his apartment?
Pretty much the entire movie hinges on Sims not knowing what his prime suspect is doing or who he's with even though he spends most of the movie in the FIRST place you'd look for him -- his own apartment.
Talk about incompetent.
Lacey was only at his apartment for a few hours after he got out of jail and before the doctor arrived per Sims orders. Therefore, it's reasonable that there were no cops there as Sims was going to send the doctor to check on him.
Plus, Sims could not have sent the doctor to the house if there were cops around as Lacey would have noticed something suspicious about the doctor coming to talk to him despite having cops around the house.