In the Police, custody police take a statement from the accused. If in the pressure of police accused writes false statement, how far it is considered valid in the Court of law.
Statement taken by the police when accused is in its custody is a protected statement and it shall not be used against the accused. According to section 26 of the Indian Evidence Act, a statement recorded by a police officer from an accused under police custody cannot be admitted against the accused. An accused is fully protected from that statement because if it is admitted against the accused then the police can make a statement or even confession from the accused either by hook or crook.
An only confessional statement is protected under this section. If accused admits any fact which tends to show his guilt or involvement in the crime, then it shall be called confessional statement and it is protected under this section.
In Mohmed Amin @ Amin C.R.M.Shaikh vs C.B.I. 2008 SCC(cri): if the accused admits his guilt before the police officer either in police custody or not, it shall not be used against the accused in any proceeding. So whether the accused made a false or true statement before the police are protected. If such a statement is adduced by the prosecution it shall be discarded by the court.
Article 20(3) of the Indian constitution also protects the right of an accused to be a witness against himself. If police officer records any statement which goes against the interest of accused such statement cannot be used against the accused because it is against the principle of self-incrimination.
You should not be afraid that that statement may be used against the accused. There is a fixed procedure in respect of the recording of statement of accused. Section 164 of the code of criminal procedure laid down method for the recording of confession. Only that confession can be used against the accused. And it is also not mandatory that accused must record his confession whenever he is being produced before the Magistrate for the recording of confession.