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I am sorry to hear about this situation. Per Colo. Rev. Stat. § 18-9-303, consent of at least one party is required to record an electronic conversation in CO. But this one party may be the same party that is recording it.
There is no exception if one party is a minor. Since one party (the DA/police) is the party of consent, that is all that is needed. (Technically, they may also have had a court order allowing them to do this, but I assume they did not - but even if they did not, the statutory law allows them to be the party of consent).
So this may be used in court.
Entrapment depends on what was said, rather than recording. Entrapment occurs when the police instigate a criminal action. For example, if an undercover agent tells a suspect "let's blow something up" - that would be entrapment on terrorist-related charges. I do not know what was said, but simply recording the conversation itself is not entrapment.
The law applies the same whether the non-consenting party is a minor or not.
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