Tape records of speeches are “documents”, as defined by Section 3 of The Evidence Act, and stands on no different footing than photographs [See, Ziyauddin, (1976) 2 SCC 17]. They are admissible in evidence on satisfying the following conditions:
(a) The voice of the person alleged to be speaking must be duly identified by the maker of the record or by others who knew it.
(b) Accuracy of what was actually recorded has to be proved by the maker of the record and satisfactory evidence, direct or circumstantial, has to be there so as to rule out possibilities of tampering with the record.
(c) The subject matter recorded has to be shown to be relevant according to rules of relevancy found in The Evidence Act.
See also, Shamsher Singh Verma v. State of Haryana, [Criminal Appeal No. 1525 of 2015] decided on 24.11.2015. Interestingly, this Shamsher quotes with approval: R.M. Malkani, (1973) 1 SCC 471.
The simplicity of Ray’s speech in R.M. Malkani:
“There is warrant for proposition that even if evidence is illegally obtained it is admissible. Over a century ago it was said in an English case where a constable searched the appellant illegally and found a quantity of offending article in his pocket that it would be a dangerous obstacle to the administration of justice if it were held, because evidence was obtained by illegal means, it could not be used against a party charged with an offence.
There is of course always a word of caution. It is that the Judge has a discretion to disallow evidence in a criminal case if the strict rules of admissibility would operate unfairly against the accused. That caution is the golden rule in criminal jurisprudence.”