CSI: 5.1

Every series has a sell by date. Some continue beyond it (X-Files) and the results look tired and stale. CSI matures with age and gives no indication of character exhaustion. If anything, the team is more comfortable in its collective skin than two seasons ago. They know each other so well, they don't have to prove anything. Now, they are family.

Things have changed, it's true, but all for the good. The rigid two-stories-an-episode formula has loosened to the point where the strongest plots are singles and the opener, Viva Las Vegas, has a three strand storyline - murder in a disco club, dead stripper in golf ball salesman's hotel suite, bathtub suicide (?) - that slip effortlessly into each other.

This maturity is enhanced by a confidence that avoids showboating. Even the affectations of Gil Grissom (William Petersen) have been toned down to an acceptable level of mild eccentricity, and personal lives, once avoided like the plague, touch the corners of an otherwise single-minded approach to evidence gathering.

Catherine's (Marg Helgenberger) daughter, who is affected by her mom's work schedule, is allowed to play a part in one of the episodes and Greg (Eric Szmanda), the lab lad with blond highlights, is endeavouring to pass the test - Grissom's high bar - to join the team as a field investigator, which becomes a running sub-plot, and the increasingly interesting Sara (Jorja Fox) exposes emotional flaws, whether alcoholic episodes in her past, or an unrequited crush on Grissom, and suddenly these super 'tecs become human and it feels right.

The cases are a mixture of tight, well-crafted mysteries (Down The Drain, Harvest) and odd, off the wall lightweights (Who Shot Sherlock, Ch-Ch-Changes), which are carried shoulder high above the critical wire by this magnificent cast. Unlike the earlier CSIs, where each episode is a detective story, in which science rules, things are happening at base that affect the entire season. The new girl at DNA can't hack it, which worries the hell out of Greg, because he recommended her. The next one, whom Warrick (Gary Dourdan) fancies, is so immune to flattery and flirting she is perfect.

The biggest surprise sneaks up on you through a number of episodes and it concerns internal politics. The team reflects Grissom's integrity and when an ambitious managerial brownnose, with next to no empathy for the department's ethos, is given the job of overall supervisor, the resulting power struggle adds another layer of intrigue into what is already beautiful and baffling.

It appears that competition from CSI: Miami and CSI: NY has stimulated the Las Vegas originals to take risks with their tried-and-tested formula. Congratulations are in order.