Records under the age of 18 can be sealed, basically they won't show up on a background screening or pre-screening with law enforcement agency-however with that being said, as a law enforcement officer you will be required to take and pass a polygraph test. If you have never had one done, its pretty simple, there is the pre-test which is more like a therapy session where you are asked a whole bunch of questions, one of which will be-ever had any trouble with law enforcement. The Polygraph examiner will more then likely not be interested in anything that happened as a kid but you still need to disclose this information, because if you don't and you feel you are hiding this information it will show up when you take the actual test (which is only about 5-10 minutes long)
Many people that go into law enforcement have stuff in their past they are embarrassed about or did wrong. The thing the agencies are looking for is honesty.
If you are looking to remove something from your public record as an adult offender, the only course of action would be to request a pardon from your governors office. Generally anything related to driving history-such as an OUI/DUI/DWI is excluded from a pardon, meaning you will never erase that information from your record. But I have processed assaults, Domestic Violence, Theft, Robbery and all that other good stuff in pardon requests before so really you can try (no guarantee it will be approved)
If the incident was minor (not a felony but a misdemeanor) it generally won't be an issue. If you have been assigned a probation sentence, then it gets a little bit tricky. General rule is, even if you manage to erase this information or hide it from sight with a spell, in the end you are going to have to disclose it during your background pre-screening, and then on your polygraph. If you don't mention it, and you are thinking about it, its gonna show up on the polygraph. Honesty is key, and learning from your mistakes and showing people you aren't perfect but you have learned from making those mistakes actually makes you stand out.