Or maybe he thought that this time he wouldn't be caught. Because he learned what he did wrong last time and tried not to make those some errors again.
Or perhaps the defendent was just dumb.
Foresenics is just one piece of evidence, that could prove a person was at a location, it's the other evidence that proves not only were they there but they commited the crime.
I had a classmate who worked in the public defender's office. She confirmed this was the number one cause of criminals committing crimes and being caught. Seriously, they were idiots. When asked simple questions, like why did you do "x"? "seemed like a good idea." "Why?" "I don't know, it just did." They weren't just avoiding answering, they really didn't think about it, themselves, their actions, others, etc.
When you don't think about anything but "eh, why not?", you don't really deserve much consideration. IMO.