All evidence is admissible in court no matter how it was obtained, legally or illegally.
Of course if you can prove that the evidence was obtained illegally you can file charges for that, but the evidence will still be used.
However, the court alone decides the value of the evidence presented, and thus the weight it places in such evidence.
Obviously statements from people suspected to be coerced in some way is not considered high-value evidence.
However just because evidence is admissible doesn't mean it has to be taken into consideration. Often the court will decide that certain evidence won't be taken into consideration due to how it was obtained. This is an entirely separate decision than whether or not it should be admissible.