Physical clues aside, the bulk of your discoveries will crop up during face-to-face interviews with suspects and witnesses. You'll choose a topic for discussion from your pad, press the interviewee, and then watch their face for a response. Depending on how the subject acts, you choose to react with one of three responses: truth, doubt or lie - the latter requiring you to produce an item of evidence to back up your claim. There's a bit of a learning curve here; it's usually fairly obvious when someone is telling the truth, but it's often harder to tell whether someone is merely being evasive (requiring doubt) or actually telling you an outright porkie pie.
The suspects in early cases give the game away quite easily, for obvious reasons, but before long you'll find yourself profiling suspects on an individual basis, contrasting their current reaction with those you've already seen. It's in this manner that you'll decide whether that young Communist agitator is glaring at you because he's telling the truth, or because he hates your guts and wants to stay clammed up.
Naturally, this kind of gameplay is only made possible by Rockstar's much discussed MotionScan technology. I'm not usually the kind of gamer who dribbles all over this kind of thing, but the fact remains that the end result here is little short of groundbreaking. Games like Uncharted 2 and Heavy Rain have already made massive leaps in this area, but after LA Noire it seems unfathomable that we’ll ever be able to sit through cutscenes packed with jerky mannequins and wooden dialogue. The quality of acting on display in a single case is enough to trump the vast majority of top-tier games; when you consider the complete selections of believably flawed miscreants - the mobsters, perverts, and barflies - there's a strong case for this being one the strongest NPC casts we've ever seen.
And yet as impressive as MotionScan is, it's arguably the underlying infrastructure that makes the game work as well as it does. I've already covered the neat design of the investigation mechanics, but there's actually a similar degree of thought behind every aspect of play. There's an in-built hint system in place, masked as "Intuition", which acts like a Raymond Chandler version of the simplifiers in Who Wants to Be a Millionaire? These powers only ever make your life easier, rather than giving you the answer outright, and their use is inherently limited. As you successfully interview suspects, complete Dispatch quests and visit landmarks dotted around the map, you'll earn XP which slowly fills a Rank meter. Level up, and you'll either earn an intuition point, or unlock some other form of reward - a new suit for Phelps, or hidden cars to find scattered about the map.
If there's one aspect of LA Noire that the hardcore will struggle with, it's this inherent accessibility. Even if you ignore the option of Intuition, this isn't a hard game. Screwing up at a crime scene or interview won't end your game, but instead force your investigation onto a different path, demanding that you find the answer elsewhere. As the case was with Heavy Rain last year, it's important to resist the gamer's instinct to reload when things do go wrong, because the ongoing struggle for the truth is what drives the game onward. Frankly, it's quite remarkable how adept the game is at cleverly shuffling its narrative threads. The very first interrogation you conduct resorts to a spot of suspect amnesia if you foul up, but from that point on it your efforts invariably feel like genuine organic detective work.
One of the very real pleasures of LA Noire is the manner in which it subconsciously teaches you to follow a set procedure. By the time you reach Homicide you'll know the drill: show up at the scene, speak to the coroner and attending officer, then take a look at the evidence before you chat to the witnesses. As subsequent clues reveal themselves, you'll make a habit of using Gamewells - roadside telephones - to call on supporting services back at HQ. You'll know that when you show up at an apartment, the mailboxes will show you whose door to kick down.