A lawsuit is not the same as a criminal trial the amount of evidence needed to find someone guilty in a civil case is much lower than that of a criminal trial. Civil court you are found guilty based on a preponderance of evidence which means something is more likely than not. Criminal trials guilt is found without a reasonable doubt which means it is absolute. Think about the OJ Simpson trial he was found innocent in criminal court yet found to be liable for damages when he was taken to civil court. So a police officer can not be fired if found liable in a civil case because the evidence is not found without a reasonable doubt.

While I'm sure we'd all love to see a bad cop fired it sets bad legal precedent to do it since that judgement can now be ruled in other cases not even involving police misconduct.