In PA the judges have at their discression the ability to convict first time DUIs with up to 24 months in prison as a maximum (yes I have seen several first hand working in law enforcement over the years). Keep in mind that this doesnt happen very often at all, but it still does none the less.
A background check for law enforcement goes back to your birth, with no gaps with references for all of it, if you have periods of time unemployed, not taking school, or whatever they ask for references in addition. In the case of a CCL the gaps are not important, but they go back to birth. I dont know the exact policies they use in each county for determining your ability to get a CCL, but they usually dont use DUI against them unless it was convicted as a felony with 2 years in prison as a maximum. I think domestic violence of any type is used as a determining factor, its specifically listed.
Worse yet, this friend of mine had to appear in court for a guy who tried to hire a hitman to kill him, none the less this guy is in state prison for the next 18 years now and this was the period of time my friend found out he couldnt get the CCL.