Training Day

The film follows a day in the life of Los Angeles Police Department officer Jake Hoyt, who is scheduled to be evaluated by Detective Alonzo Harris, a highly decorated LAPD narcotics officer. In Alonzo's car, the officer sees teenage Mara Salvatrucha gang members dealing drugs in a park. Alonzo confiscates the drugs and tells Jake to take a hit of the marijuana. Jake refuses but Alonzo puts a gun to his head and says that Jake's failure to use drugs could get him killed by a street dealer.
Jake relents and smokes the marijuana. Alonzo then tells him the marijuana was laced with PCP. While driving, Jake notices a female high school student named Letty being sexually assaulted. Jake subdues the attackers while Alonzo watches. Alonzo tells Letty to leave. Jake objects but Alonzo says that street justice has been served after taking the men's money and crack and that Letty's cousins will most likely take further revenge. Jake finds Letty's wallet on the ground and takes it.
Later on, Alonzo and Jake apprehend a wheelchair-bound drug dealer named Blue and find crack rocks and a loaded handgun on him. In exchange for his freedom, Blue reveals his associate: Kevin "Sandman" Miller, who is in prison. Alonzo takes Jake to Sandman's home in Watts, where he uses a fake search warrant to steal drug money from the premises. However, Sandman's wife notices the warrant is fake and calls out to the nearby Crips gang members who open fire. The two barely manage to escape and an irate Jake objects to Alonzo's actions.
The duo visit Alonzo's Salvadoran mistress Sara and their young son at Baldwin Village. Afterward, Alonzo meets with a group of high-ranking police officials dubbed as the "Three Wise Men." They tell Alonzo that they know he owes money to the Russian mafia and suggest that he leave town. Alonzo insists that he has control of the situation and gets permission to "cash in on an account." Later, Alonzo tells Jake that he had to give Sandman's money to the Three Wise Men in order to obtain the unjustified arrest warrant.
Alonzo takes Jake and four other narcotic officers to the home of Roger, a drug dealer and former police officer the duo had visited earlier. Using the warrant, they seize several million dollars from underneath the floor of Roger's kitchen; Jake refuses to take his share of the cash. Alonzo kills Roger and arranges for the scene to appear like a justified shooting. But Jake refuses to lie and after being threatened, seizes Alonzo's shotgun. A Mexican standoff ensues. However, Alonzo calms his associates and claims that the LAPD will run a blood test on Jake (identifying the PCP from the marijuana), the result of which he can falsify in exchange for Jake's cooperation. Jake reluctantly agrees.
Alonzo drives Jake to the home of a SureÃ±o named "Smiley," allegedly to run an errand. He furtively abandons Jake as Jake reluctantly plays poker with Smiley and his fellow gang members. A tense conversation ensues in which Smiley reveals Alonzo's situation: by midnight, Alonzo must pay $1 million to the Russian mob for killing one of their couriers in Las Vegas or be killed himself. Jake realizes too late that Alonzo had paid Smiley to kill him and is subdued and dragged to the shower. There, the gang finds the wallet dropped by Letty, who is revealed to be Smiley's cousin. Smiley calls Letty to confirm Jake's story and she confirms that a police officer risked his life to defend her. In gratitude for protecting his cousin, Smiley lets Jake go.
As he returns to Sara's apartment to look for Alonzo, Jake endeavors to arrest Alonzo, but a gunfight ensues inside the apartment. Jake then begins to pursue Alonzo on the rooftops of the apartment where a fistfight ensues between the two before Alonzo is able to escape to his vehicle. Jake eventually is able to subdue Alonzo in his vehicle, after which the local Bloods gang members and residents begin congregating to watch. Alonzo tries to get the crowd on his side by offering a reward to whoever kills Jake, but they have grown tired of Alonzo's arrogance and corruption and allow Jake to walk away with the money (which he intends to use as evidence in turning in Alonzo). Alonzo attempts to escape via Los Angeles International Airport, but is killed by the Russian mafia hitmen in a street shooting. Later on, Jake listens as Alonzo's death is broadcast over the news, touting him as a heroic officer.

Question: Who wallet does Jake find on the ground ?
Answer: Letty's.