Phoenix Wright question

I've been wanting to get into the Ace Attorney series, and I want to start with Dual Destinies. But then I saw that it's rated M. Is the mature content too bad? And if it is, what other title should I start with?

It's mainly just blood that pushes it up there, you should be fine. I'd personally start from the beginning, but Dual Destinies is a good game to start with, too. Not much need to play the other games with that, bar maybe Apollo Justice.

I personally reccomend playing the whole series before playing DD if you want to get a full understanding/all the referances but it won't be too hard to understand if you play DD first, but like Icemario said, its good to at least play AJ first.
It's mostly blood and the dark theme which makes it M rated.