Some potential evidence gathered in the sniper case:
A piece of paper at the scene of an Alabama shooting bearing the fingerprint of John Lee Malvo, 17, a source told The Sun. Police traced Malvo to a Tacoma, Wash., home where he had been living with John Allen Muhammad, 42.
A caller to the sniper investigation tip line apparently claimed responsibility for the sniper shootings and the Sept. 21 shooting in Montgomery, Ala., in which one woman was killed and another wounded, Montgomery Mayor Bobby Bright said.
In Alabama, Montgomery Police Chief John Wilson said a composite sketch of a suspect in a Sept. 21 liquor store shooting, who was almost caught by police officers in a foot chase, has "very good similarities" to Malvo.
A tree stump taken from the Tacoma, Wash., home where Muhammad and Malvo once lived. Sources said the stump might contain bullets or bullet fragments. Investigators also reportedly searched the home for samples of Malvo's handwriting.
The blue 1990 Chevrolet Caprice in which the two people were arrested is registered to Muhammad at an address in Camden, N.J., according to the New Jersey Department of Motor Vehicles.
Ballistics tests of recovered bullet fragments or casings have determined that .223 caliber bullets were fired from the same rifle, but they may not tell police which individual rifle was used.
Handwritten notes believed to be from the sniper can be analyzed for language patterns, spelling, distinctive penmanship and more.
The paper used by the writer can be checked for fingerprints, DNA evidence, fibers and more, as can anything found at the sniper's crime scenes.
Phone calls apparently from the sniper can be checked for speech patterns, a distinctive accent or anything recognizable to those who know him.
Sniper's request for a special toll-free number to speak with police, his demand for money and the calls already made to police might tip them off to his location.
Scattered eyewitness reports have led police to distribute sample images of possible getaway vehicles: a white box truck, a white, late model Chevy van with a top rack and a white or very light Ford Econoline van, also a late model with a top rack. But they have not ruled out other vehicles.
A caller to the sniper investigation tip line apparently claimed responsibility for the sniper shootings and the Sept. 21 shooting in Montgomery, Ala., in which one woman was killed and another wounded, Montgomery Mayor Bobby Bright said.