I want to unpack this a bit.You make an effort to glean clues from a creature's body language, speech habits, and changes in mannerisms in an attempt to search out a lie. If the outcome of that effort is uncertain and there's a meaningful consequence for failure, make a Wisdom check. If you're proficient in Insight, add your proficiency bonus to the check.
Page 61 of the Basic PDF says "A Wisdom check might reflect an effort to read body language, understand someone’s feelings, notice things about the environment, or care for an injured person." And page 58 says "The DM calls for an ability check when a character or monster attempts an action (other than an attack) that has a chance of failure. When the outcome is uncertain, the dice determine the results."
Putting these together, it seems that the following is true:
If a player declares that his/her PC attempts to read body language, understand someone’s feelings, notice things about the environment, or care for an injured person, and if the GM takes the view that that action by the PC has a chance of failure and/or an uncertain outcome, then the GM should call for a WIS check to determine the result of the character's action.
Now, page 62 says that "Your Wisdom (Insight) check decides whether you can determine the true intentions of a creature, such as when searching out a lie or predicting someone’s next move. Doing so involves gleaning clues from body language, speech habits, and changes in mannerisms."
Putting that together with the above, we get:
If a player declares that his/her PC attempts to glean clues from body language, speech habits and changes in mannerisms, so as to understand someone's feelings and true intentions (including where these pertain to telling a lie or to the being's next move), and if the GM takes the view that that action has a chance of failure and/or an uncertain outcome, then the GM should call for a WIS (Insight) check to determine the result of the character's action.
Some resulting complexities inlcude: on what basis ought the GM to take the view that the action has a chance of failure and/or an uncertain outcome?
There seem to be few cases in which a player would declare such an action and success be automatic: eg if the GM narrates that a NPC is rolling around in laughter, or has tears streaming down his/her face, then either the player would know why (because it's been already communicated in play) and hence not declare this sort of action, or else the cause of the mirth or the upset would be uncertain to the player, in which case I find it hard to think of a scenario (given my conception of how RPGs are normally played) in which the PC would be certain simply by studying the body language etc of the NPC.
It's quite conceivable, on the other hand, that there could be many cases where there is no chance of success - eg if an NPC is as inscrutable as the sphinx - but on the other hand the very presence of the rules for WIS and WIS (Insight) checks in the game seems to imply that actions of this sort might sometimes succeed, and it would seem a bit of a hosing for the GM to rule very frequently that this or that NPC is too inscrutable to be "read".
Here's another complexity: what should we take to be the result of such an action, if successful? Presumably it's not that the PC knows the NPC's body language. That's what is read; it's not itself the reading. Presumably it's either the clues (which is perhaps what the Insight description on p 62 points towards) or its the feelings and true intentions (which is perhaps what the WIS check description on p 61 points towards). I certainly think the language on p 62 ("such as when searching out a lie or predicting someone’s next move") indicates that the feelings, true intentions etc which the character is (as per p 61) attempting to "understand" might include an intention to lie/deceive or an intention to make this or that next move.
So whether or not Insight can be used to determine that a NPC is speaking with the intention to lie deceive seems to me to turn on whether the table takes the result of these sorts of actions to be gleaning certain clues or understanding certain intentions/feelings to which the gleaned clues point. Given the ambiguity in this respect between pp 61 and 62, I think a table could reasonably run it either way. Personally I would favour the second of those approaches, because generally I think a RPG works better when players are able to declare actions that (if they succeed) substantially improve their PCs' positions. And I worry that simply telling the player the clues may not add very much to what a savvy player can discern from the GM's framing of the situation, which seems to make declaring the action (and hence risking whatever consequences might flow from failure) somewhat pointless.