How did they prove Cody killed Jason after searching Jason's history?

True, hacking into the computer was stupid. (Plus, it was unbelievable they way the hacker did it.)

But the pad was only shown to the police. The police would have understood the pad was useless as evidence. But they would have pulled the phone records and found the call from the pharmacy to Cody's cell phone. Perhaps even found a pharmacy employee who remembered Cody since Cody would've had to visit the pharmacy twice - once to drop off the prescription and once to pick it up. Or perhaps he phoned it in, in which case, his phone call would also be logged. And perhaps his prints were still on the prescription.

Ahhh, there are so many pieces of evidence, the mind boggles. Don't forget the police also said "we just need one hair to place her at the scene." The boys weren't prepared for a cover up and even when they were planning the 2nd murder, they weren't thinking things through.

Except that hacking into someone's computer would have gotten the evidence thrown out in court. The evidence was tampered with.