Alison's Attempted Killer

Alison's killer is currently unknown.

Suspects

 * Toby Cavanaugh (Cleared [Legally])
 * Ian Thomas (Cleared)
 * Garrett Reynolds (Cleared [Legally])
 * Byron Montgomery (Cleared)

Guesses
The Liars first suspect Toby Cavanaugh because Ali was wearing his sweater on the night she died. They thought that Toby was Alison's secret boyfriend, and that he killed her. They later clear him because of him admitting to Emily that his tattoo, '901 Free at Last', was the day that he was free from his forced relationship with Jenna, rather than the day Ali was killed.

The next suspect was Ian Thomas, because of his secret relationship with Alison, and because of a misunderstanding in the Kissing Rock video. He is later cleared, as the girls are shown the rest of the video by A, which shows that Alison and Ian both left the Kissing Rock after the video ended.

Garrett Reynolds is then accused of murdering both Alison and Maya St. Germain, because Jenna handed back page 5 of Alison's autopsy report, which Garrett had stolen and given to her. He was also accused because Maya was sighted getting into his car the night she died. However, Garrett was cleared after it was discovered that Lyndon James actually killed Maya, and Garrett had told Spencer what he saw and heard the night that Ali died.

Byron Montgomery was thought to be involved in Ali's murder because Garrett saw them talking the night that Ali died. Through Alison's diary, it is discovered that Ali was blackmailing Byron for money in order for her to keep quiet about Byron's affair with Meredith, and Byron is cleared.