Was the police biased?

Why didn't Serena insist to the police what was the true?
Did Serena really withhold information from the police?
She did say that Massi didn't do it.They were very insistent with the idea that Massi did.

I have various questions regarding your opinion on this issue, answer at your own discretion :

-Do you think it counts as obstruction of justice and similar offenses?

-Do you think that malicious cop would agree immediately if she said that some poor kid drove the 4x4 and hit the cyclist?

-Do cops in these countries get some kind of reward by getting rich kids to jail? Does this get them more respect from italian society or something?