Prosecutor Juan Martinez previously argued Arias planned the murder, and stole a .25-caliber gun from her grandmother in California to kill Alexander, who had been her boyfriend.
Arias -- who initially pleaded not guilty, but testified Feb. 6 she killed Alexander -- said Tuesday she used Alexander's gun, and only meant to point it at him to keep him from abusing her, KTVK-TV, Phoenix, reported.
Martinez argued Arias flipped her car's license plate during her road trip from California to Arizona to avoid detection, but Arias said she saw kids in a store parking lot tampering with the plate.
Arias was to answer the jurors' 100 questions of her Wednesday afternoon, The Arizona Republic said. The newspaper said attorneys were to read the approved questions to Arias at 1 p.m. MST.
Arias, 32, has spent 15 days testifying, ABC News reported, describing her sex life with Alexander, who was 30 when he was killed at his Mesa home in June 2008.
The defense hopes to convince the jury Arias was defending herself after months of strange sexual encounters and abuse when she stabbed Alexander 27 times, slashed his throat and shot him twice in the head, ABC News said.