A Case Study on Logic Puzzles

Module 03 Case Study – Logic Puzzles 1. A computer store was robbed over the weekend, and the police have rounded up four suspects. The detective interrogated them and determined that one of them was indeed the robber. Here were the statements:
Shirley: Dennis did it.
Dennis: Alan did it.
Brad: I didn't do it.
Alan: Dennis lied when he said that I did it.
Only one of these four statements is true. With that in mind, who is the guilty party?
I am thinking that the robber is Brad. None of the others said he did it, they blamed everyone else but him. Brad himself didn’t blame any one of the others but did say he didn’t do it. These reasons would lead me to think it was Brad. 2. Shepard was found murdered one night in a back alley. The next day, the police rounded up three suspects, who were interrogated by the toughest detective around, Carly Hearn. The suspects made the following statements to her:
Garrus:
1. I didn't kill Shepard 2. Ashley is not my friend. 3. I knew Shepard.
Ashley:
1. I didn't kill Shepard. 2. Garrus and Talia are friends of mine. 3. Garrus didn't kill Shepard.
Talia
1. I didn't kill Shepard. 2. Garrus lied when he said Ashley was not his friend. 3. I don't know who killed Shepard.
Only one of these suspects is guilty, and only one of each man's three statements is false (the other two being true). Who did Detective Hearn correctly arrest for the crime?
I think Talia was arrested for the crime. Talia didn’t mention that Garrus or Ashley did it, just denied knowing. Ashley claimed to be both of their friends but stood up for Garrus by stating He didn’t do it, which points the finger at Talia without actually doing so. Talia was the only one who denied knowing who did it, while Garrus and Ashley claimed not to of done