Couldn’t have robbed/couldn’t rob//had been/was---verb tense?

[z7655431]

Then, the next day a man who was suspected of robbing a jewelry store was caught by other colleagues, but the suspect insisted that he “couldn’t have robbed” the jewelry store because he “had been” in a completely different neighborhood that night, breaking into a cell phone shop.
In the first quotes, can I say "couldn’t rob" instead of “couldn’t have robbed”? In the second quotes, can I say "was" instead of "had been"? Which verb tense is better?

 

[bhaisahab]

It's fine as it is. It wouldn't be wrong with "couldn't rob" and "was", but the meaning would be different.

 

[Raymott]

With the probably intended meaning, "couldn't have robbed" is necessary. You could use either for the second. I'd use 'was'.