To what extent is it permissible to use truth serum and the polygraph in criminal investigations with the accused?

Scholars have differed regarding the ruling on using a lie detector. The preponderant opinion is that its use is prohibited because of the harm it causes to the accused, except in cases of extreme necessity and according to specific regulations: such as the permission of the guardian (ruler), the seriousness of the crime, the existence of strong circumstantial evidence, that the accused is in good health, that the operator is an expert, and that the results of the device are considered circumstantial evidence, not conclusive proof.

As for truth serum, its use is prohibited due to the narcotic substances it contains and the harm it causes to the accused, and any confession resulting from it is not considered valid.