A rule of thumb for TV series: You can tell which actors the writers trust by seeing who carries the exposition.
The actor who explains the stuff that’s necessary for the viewer to understand — that’s the one the writers depend on. It’s hard for an actor to make the whos, hows, and whens of a story interesting, especially in crime shows where the audience has to understand technical data ranging from the analysis of skin-oil chemistry to the intricacies of the Russian Mafia. And when an actor can do it, he or she is pure gold to the writers.
The expository actor may not be the best performer on the show, but he or she is often the most reliable. And often older than the star. And, for some reason, likely as not British: David McCallum on NCIS, Anthony Stewart Head on Buffy the Vampire Slayer, John Noble on Fringe, Amanda Tapping on Stargate SG-1, Edward Mulhare on Knight Rider (for those of us with long memories).