I've realized that most, if not all current veteran inmate characters aren't roleplayed very differently from fresh inmates when it comes to the language used. On most prison yards across the U.S. above a Level 2, the way inmates speak to each other is rather distinct and might be surprising to people on the outside looking in.
We all know that people who grow up in a low income environment and spend a lot of time on the streets, e.g. gangbangers, tend to swear a lot and casually disrespect each other all the time, paying it no mind. This changes in prison though because prison is all about respect, and one of the primary ways through which respect or a lack of respect is demonstrated is the way people speak to each other. Experienced inmates speak very respectfully to each other, even if they are from rival cars. They tend to take a very old fashioned and conservative view of swearing, i.e. there's not really such a thing as casual swearing and to use 'offensive language' is genuinely considered offensive.
The progression of the average Level 4 inmate's vocabulary would probably go something like this in my mind: An inmate who's been in prison for about two years has probably started to use curse words and generally offensive language a lot less. Words like 'punk' and 'bitch' are included under this, and there is no casual way to use these words. If you call someone a punk you're basically calling them out and probably challenging them to a fight. An inmate who's been in prison for five years has probably began to use a lot less slang and speaks in a rather mature way. Some may not even use contractions anymore (e.g. "do not" instead of "don't"). An inmate who's been in prison for more than ten years can often have a rather developed vocabulary, using complex language and having high-brow discussions. Their development only progresses from here. On the other hand don't make the mistake of thinking that people like Rene Enriquez are common even in the elite ranks of the Mexican Mafia. While he's not a unique individual, somebody with his inherent eloquence and arguably inherent intelligence is certainly rare and probably only a few of the most senior carnales are alike to him.
My reasoning for this phenomenon of language development among prisoners is a) initially they adapt to the respectful environment demanded by yard veterans, thus stop swearing and using other disrespectful language and b) most programs require their members to read actively, it's considered as important as working out. After 10 years of studying constantly, I imagine inmates learn a lot - including words and how to use them. For younger inmates, studying for and getting their GED probably also contributes to this.
I suggest people start putting some thought into how their character would speak based on their prison career. I've slacked off a bit in this department myself.
