Sarah Coletti is a police officer who was found by the group on the road. She and three more policemen took a small group of refugees out of the heavily infested neighborhoods to safety, but they merged with the scientists' group when they met.
Sarah is a trained officer with good aim. Her training however is less than the military members of the group, which make sher weaker. She can use a gun with ease, but slowly she learns to shoot other weapons too, because a gun is unable to save her in case of an alien attack. She is most often friendly and talkative, while retaining some seriousness at all times.
When they find the community, Sarah is useful because she is the only former policeman there and helps keep the peace. She helps a lot because William doesn't seem to do well at it, since he doesn't have any experience with law breaking, etc. Sarah is more patient though and willing to bend the rules in order to preserve the peace, and often looks the other way when William doesn't. She comes at odds with William over this when someone is found smuggling drugs inside the community, and William wants to arrest them and take the drugs, but Sarah wants to let them do their business on the condition they do it quietly. William doesn't accept this, but Sarah makes him think what will happen if some junkies are cut off from their drugs. She tells him to use his head for a while and look at what's real and not what his moral says. She also tells him to listen to her, since she has lived these things all her life. She continues saying that cops like her may bend thee rules, may allow things that shouldn't happen, but in the real world, sometimes you have to choose between the bad and the worse. If that makes her a bad cop, then so be it.
She and her group are found after the group leaves the village heading for New York. They were heading there as well, and that's how the group finds out about the deadlands.