Sue Ellen was a young girl who lived in Judge Catherine Lavinio's neighborhood. Every night she walked her dog past the judge's house. One night during her walk, she heard the smoke alarm go off at the Judge's house. Looking at the house, she saw a "very fat man" open the curtains, then stand on a chair to turn off the smoke detector. Sue Ellen could not make anything else about him other than his immense size.
She learned the next day that the Judge had been murdered, apparently by the fat man. She spoke to not only the police but Adrian Monk (after forcing him to buy two cups of lemonade at her stand) and what she told him helped Monk piece together that the crime scene had been staged.