If a police officer is not always alert and ready to act they could be unprepared for a situation that they could encouter. Furthermore, if a police officer isn't alert and ready, a police officer may miss something that could compromise their safety, or miss an offense that occurs in front of them.
alert
ready and alert
If you are "alert" you are awake and and ready for things - feeling sharp.
Alert
Be alert, as if you were ready to run.
Police officers are ready to battle at night. The officer who guards the statue in Backlot's Mansion takes a break between 2 and 3 AM.
The alarm clock rang loudly to alert him that it was time to wake up.
ALERT
Yes, if you know of one, report them... BUT... be ready to back up your allegations with supportable facts. PO's, just like police officers, are subject to a lot of false allegations made against them in an effort to intimidate them into "laying off" people.
quick, attentive, alert, fast, sharp, active
Bonesaw is always ready
RAAF Air Command's motto is 'Alert and Ready'.