I'm sure we can make a framework around when they can lie. They can not lie to obtain facts or information while investigating. Doing so should poison what they gain and anything found afterwards.
> should poison what they gain and anything found afterwards.
That's a more expansive proposal than the law being discussed. The law is narrower than "investigating" and is focused only on interrogating a suspect, so presumably post-Miranda warning. And in this context being a "suspect" is a specific category elevated from being a witness or person of interest. And then the only penalty in the law is making a confession obtained as the result of a lie to a suspect during an interrogation inadmissable.
Those differences address the concerns mentioned downthread with lying in the context of undercover work.
Frankly the nickle-and-diming of when Miranda does and does not apply is itself an issue: "Oh, no, you're not under arrest, you're just being detained indefinitely," "Hahaha a dog practicing law? What an idiot, continue the interrogation," and "Your honor, the suspect failed to verbally affirm his right to remain silent; instead simply not speaking, so we were under no obligation to cease attempting to interrogate him" are all arguments that the Supreme Court has, in its infinite wisdom, seen fit to uphold as not violating Miranda.
That's an easy situation to deal with. Have someone who isn't an officer sit at the computer and pretend they are a 12 year old girl to catch a child predator and turn the evidence over to the non-lying police.
That's a more expansive proposal than the law being discussed. The law is narrower than "investigating" and is focused only on interrogating a suspect, so presumably post-Miranda warning. And in this context being a "suspect" is a specific category elevated from being a witness or person of interest. And then the only penalty in the law is making a confession obtained as the result of a lie to a suspect during an interrogation inadmissable.
Those differences address the concerns mentioned downthread with lying in the context of undercover work.