A single bench of Delhi High Court held as follows, wrt usage of section 91 Cr.P.C.

From Para 14,

14. The Division Bench of Hon‟ble High Court of Madhya Pradesh in case of Special Police Establishment v. Umesh Tiwari 2022 SCC OnLine MP 100 had enlisted the ingredients of Section 91 of Cr.P.C., and had also observed that the right to invoke Section 91 is not limited only to the Court and Police, but also to the victim, accused and/or any other stakeholder. The relevant observations are reproduced hereunder for reference:
“4.3 Language employed in Section 91 reveals following foundational ingredients and characteristics:-
(i) Section 91 is meant to be invoked for producing documents/other things by way of summon.
(ii) Section 91 can be invoked at any stage of investigation, inquiry, trial or even other proceedings under the Cr.P.C.
(iii) Section 91 does not expressly provide as to who can invoke this provision.
(iv) However, the language of Section 91 implies that it can be invoked by the Court or the Officer in-charge of the Police Station concerned.
(v) And this invocation can be done when the Court or the Police is of the view that production is necessary or desirable for the purpose of investigation, inquiry, trial or other proceedings under Cr.P.C.
(vi) The satisfaction regarding necessity or desirability of the Court or the Police is sine qua non for invoking this provision.
(vii) The production of document or other thing is to be made before the Court if directed by the Court or before the officer if directed by Police Officer. ***
4.5 From the aforesaid analysis, it is vivid that it would not be proper to restrict the right to invoke Section 91 to only the Court and the Police Officer. The window of Section 91 will have to remain open for all the stakeholders in an investigation, inquiry, trial and other proceedings, be it the victim, accused, police, Court or any other stakeholders involved.

From Para 15,

15. The Hon’ble Apex Court in case of Debendra Nath Padhi (supra), while examining the issue of when an accused would be entitled to file an application under Section 91 of Cr.P.C., had discussed the concept of “necessity‟ and “desirability‟ of production of a document or any other thing. The relevant observations of the Hon’ble Apex Court read as under:
“25. Any document or other thing envisaged under the aforesaid provision can be ordered to be produced on finding that the same is “necessary or desirable for the purpose of investigation, inquiry, trial or other proceedings under the Code”.
The first and foremost requirement of the section is about the document being necessary or desirable. The necessity or desirability would have to be seen with reference to the stage when a prayer is made for the production. If any document is necessary or desirable for the defence of the accused, the question of invoking Section 91 at the initial stage of framing of a charge would not arise since defence of the accused is not relevant at that stage. When the section refers to investigation, inquiry, trial or other proceedings, it is to be borne in mind that under the section a police officer may move the court for summoning and production of a document as may be necessary at any of the stages mentioned in the section. Insofar as the accused is concerned, his entitlement to seek order under Section 91 would ordinarily not come till the stage of defence. When the section talks of the document being necessary and desirable, it is implicit that necessity and desirability is to be examined considering the stage when such a prayer for summoning and production is made and the party who makes it, whether police or accused…”