Besides Felicia "Snoop," Pearson, here's a partial list of main characters that also meet the description:

https://en.wikipedia.org/wiki/Donnie_Andrews

https://en.wikipedia.org/wiki/Melvin_Williams_(actor)

https://en.wikipedia.org/wiki/Ed_Norris

https://en.wikipedia.org/wiki/Gary_D%27Addario

https://en.wikipedia.org/wiki/Jay_Landsman

https://en.wikipedia.org/wiki/Richard_Burton_(Baltimore)

https://en.wikipedia.org/wiki/Steve_Earle

https://en.wikipedia.org/wiki/William_F._Zorzi

https://en.wikipedia.org/wiki/Anwan_Glover

And don't forget the show's creators:

https://en.wikipedia.org/wiki/David_Simon - former journalist at the Baltimore Sun.

https://en.wikipedia.org/wiki/Ed_Burns - former Baltimore police and public school teacher.