Legal Question in DUI Law in District of Columbia

I am not sure what you mean by retroactively. Typically you are informed of your court date upon arrest in DC.

Can the cops decide not to arrest you, and then have charges filed later? Yes! Can you crash your car while drunk, nobody knows who you are, and then the investigation leads to you as the driver and there's some evidence you were drunk and you get charged? Yes! Then it's your job to get a lawyer and defend it, argue speedy trial, etc.