A Full Bench of the Apex Court passed these broad factors while considering transfer petitions u/s 406 Cr.P.C.

From Para 24,

24.Thus, although no rigid and inflexible rule or test could be laid down to decide whether or not power under Section 406 of the Cr.P.C. should be
exercised, it is manifest from a bare reading of sub-sections (2) and (3) of the said Section and on an analysis of the decisions of this Court that an order of transfer of trial is not to be passed as a matter of routine or merely because an interested party has expressed some apprehension about the proper conduct of a trial. This power has to be exercised cautiously and in exceptional situations, where it becomes necessary to do so to provide credibility to the trial. Some of the broad factors which could be kept in mind while considering an application for transfer of the trial are:-
(i) when it appears that the State machinery or prosecution is acting hand in glove with the accused, and there is likelihood of miscarriage of justice due to the lackadaisical attitude of the prosecution;
(ii) when there is material to show that the accused may influence the prosecution witnesses or cause physical harm to the complainant;
(iii) comparative inconvenience and hardships likely to be caused to the accused, the complainant/the prosecution and the witnesses, besides the burden to be borne by the State Exchequer in making payment of travelling and other expenses of the official and non-official witnesses;
(iv) a communally surcharged atmosphere, indicating some proof of inability of holding fair and impartial trial because of the accusations made and the nature of the crime committed by the accused; and
(v) existence of some material from which it can be inferred that the some persons are so hostile that they are interfering or are likely to interfere either directly or indirectly with the course of justice.

Nahar Singh Yadav and Anr Vs Union of India and Ors on 19 Nov 2010

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Citations : [2011 AIR SC 1549], [2011 RCR CRIMINAL SC 1 120], [2011 SCC CRI 1 39], [2011 AIR SC 325], [2011 SCC 1 307], [2010 AIOL 798], [2010 SLT 9 322], [2010 JT 12 641], [2011 CRLJ SC 997], [2010 SCALE 12 199], [2010 SUPREME 7 729], [2010 AIC 96 1], [2011 ECRN 1 717], [2011 KCCR 2 845], [2011 AIR SCW 325], [201 OJ 13 (ADDL.) S.C.R. 851]

Other Sources:

https://indiankanoon.org/doc/668282/

https://www.casemine.com/judgement/in/5609aedde4b0149711414eec

https://vlex.in/vid/nahar-singh-yadav-and-572148534

https://www.latestlaws.com/latest-caselaw/2010/november/2010-latest-caselaw-867-sc/