Seasons 2, 3, and 4 of Southland aired on TNT when the show was picked up after NBC cancelled it. Southland The Complete Second, Third, and Fourth Seasons Uncensored features a total of 26 episodes and various behind-the-scenes and unaired scenes as special features. Though focused on fewer main characters than Homicide, not as dark as The Shield, and not always as even or well-written as either, there are similarities between this TV cop show and those excellent series.
Starting with season two Southland focuses on fewer characters. These are rookie cop Ben Sherman and Officer John Cooper, Detective Lydia Adams, Detective Sammy Bryant, and starting season 4 Officer Jessica Tang (Lucy Liu).
Southland is not particularly different from your usual TV cop show except perhaps that it focuses on both detectives and officers and work and personal life. The show has some continuing story threads so you can be a bit confused if you skip an episode but an episode's main story line is self-contained. At the same time, changes are made without explanation such as Lydia having a new partner episode 4 season 2.
Southland Season 4 is the best of the three offered here. It also has Lucy Liu as a cop partnered with one of the regulars. Yes, that is Marla Gibbs (Florence on The Jeffersons and Hattie Mae Hughley) in episode 2.
A cool thing about Southland Seasons 2 to 4 is season 4 ends with the main storylines closed so you do not need season 5 to figure things out.
Whoever decided to change the series' opening theme starting season 3 was a moron.