Felons and police officers seem to belong in two completely different boxes. Felons are criminals convicted of the most serious types of crimes and offenses that can result in jail sentences of more than a year. Cops are the law enforcement folk charged with locating and arresting the bad guys. Anyone reading the news knows that it is possible for a cop to become a felon. But can a felon become a cop?
Generally, it is not possible for someone convicted of a felony to become a police officer. Aside from obvious public-trust issues, felons cannot legally own or use guns.
Each state sets its own requirements for candidates wishing to enter law enforcement. State laws may be all over the map on many issues, but on one they are uniform: anyone convicted of a felony is not eligible to work as a police officer. One obvious reason for this rule is that police officers are supposed to have integrity and good judgment. Someone who fell deep enough into a life of crime to be convicted of a felony does not appear likely to have those characteristics. This is true even if you committed the crime when you were a juvenile.
Second, police officers carry guns and must be able to defend themselves and the public with firearms. Felons usually lose the right to own or use guns for their lifetimes. Federal law prohibits felons from carrying, shooting, holding or owning a gun. It is also against the law for a felon to buy any type of ammunition. That means breaking into law enforcement would be very difficult for a felon.
In addition, police officers often appear as witnesses in the criminal prosecutions of criminals they aided in arresting. Defense attorneys are legally charged with defending their clients in every legitimate way possible, and this includes cross-examining police who testify at trial. The jury hearing the case may not have confidence in the testimony of a police officer who was, earlier in life, convicted of a serious crime.
Does a felony arrest also make someone eligible to be a police officer? Not to the same extent as a conviction. However, a felony arrest is unlikely to be overlooked in any state. The Police Department does a thorough background investigation before admitting candidates to the police academy and will surely find the arrest. They will make their own determination. If it was a clear case of mistaken identity, you'll probably be alright. Remember that getting into law enforcement is very competitive and that there are lots of candidates with clear criminal records you are competing against.
All expungements are not created equal. In all states, expungement gets rid of an offense to a greater degree than just sealing the record. But some states physically destroy the records, while others simply make them unavailable.
In most states, you do not have to admit the existence of an expunged conviction. But in many states there is an exception for law enforcement, who will be able to access otherwise unattainable records. Read the expungement laws in your state and talk to an attorney to determine whether or not you can deny the existence of the felony conviction on a police officer application. Lying on the application may itself disqualify you.
In some states, like California, you are not eligible to become a police officer if you have been convicted of a felony. No exception is made for those with an expunged felony conviction.