Well, every time I take a wrong turn in it I end up immediately in the ghetto, but that might just be my crackdar.
That’s because you’re on the wrong side of Calhoun! Flee! Flee the ghetto! All the way south of Broad if you really want to be safe! 
The above link is every boring thing you might ever want to know about Charleston.
From personal experience, I have always FELT safe in Charleston, regardless of whether I was in the ghetto, North Charleston, or wherever. I’ve felt safe parking and leaving my car (granted it’s not a very nice car, and I wouldn’t leave my purse or valuables on the seat or anything stupid like that) and I’ve also felt safe walking around just by myself at all times of the day and night (weedy white girl here).
I don’t know if that translates into objective safety, but I HAVE felt unsafe in places before, and Charleston just doesn’t have that ‘dangerous’ vibe to me.
I just moved from Charleston this summer. I hated it, there is nothing that could make me move back there. I won’t bore you by going through all the reasons but I will agree with the very good advice someone has already given you that you should go stay there for a month or so in the summer. Don’t just go do touristy things, try and drive around, go grocery shopping, do day to day living things and see what you think.
To answer your question Charleston does have a high crime rate, I forget what it is per capita but I am sure you could find it if you were interested. I’ll share some person experiences. Two men attempted to carjack my husband just outside the military base. Someone tried to kick down the front door to our house when I was home alone during the middle of the day. Someone tried to carjack a woman waiting at the light in front of me at the local walmart. Multiple times the school five minutes away from our house had to be locked down because someone was threatening people with a gun. We never had a car stolen but we did have personal property taken including a pet that some kids attempted to beat to death with a rock. Well I say kids but it was three 7 year olds and a 22 year old sex offender who lived in the neighborhood with his sister and hung around the kids. There are multiple parts of the city we were asked, by the military, not to go to after dark.