Supreme Court explained the Section 6 of Evidence Act.

Section 6 of the Evidence Act is an exception to the general rule whereunder the hearsay evidence becomes admissible. But for bringing such hearsay evidence within the provisions of Section 6, what is required to be established is that it must be almost contemporaneous with the acts and there should not be an interval which would allow fabrication. The statements sought to be admitted, therefore, as forming part of res gestae, must have been made contemporaneously with the acts or immediately thereafter. The aforesaid rule as it is stated in Wigmores Evidence Act reads thus: Under the present Exception [to hearsay] an utterance is by hypothesis, offered as an assertion to evidence the fact asserted (for example that a car-brake was set or not set), and the only condition is that it shall have been made spontaneously, i.e. as the natural effusion of a state of excitement. Now this state of excitement may well continue to exist after the exciting fact has ended. The declaration, therefore, may be admissible even though subsequent to the occurrence, provided it is near enough in time to allow the assumption that the exciting influence continued.

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Sarkar on Evidence (Fifteenth Edition) summarises the law relating to applicability of Section 6 of the Evidence Act thus:

1. The declarations (oral or written must relate to the act which is in issue or relevant thereto; they are not admissible merely because they accompany an act. Moreover the declarations must relate to and explain the fact they accompany, and not independent facts previous or subsequent thereto unless such facts are part of a transaction which is continuous.
2. The declarations must be substantially contemporaneous with the fact and not merely the narrative of a past.
3. The declaration and the act may be by the same person, or they may be by different persons, e.g., the declarations of the victim, assailant and bystanders. In conspiracy, riot &c.the declarations of all concerned in the common object are admissible.
4. Though admissible to explain or corroborate, or to understand the significance of the act, declarations are not evidence of the truth of the matters stated.