Supreme Court held that the necessary ingredients to make out a IPC 306 offence are missing in the case.

From Para 15, Mental Cruelty,

15. The concept of mental cruelty depends upon the milieu and the strata from which the persons come from and definitely has an individualistic perception regard being had to one’s endurance and sensitivity. It is difficult to generalise but certainly it can be appreciated in a set of established facts. Extra-marital relationship, per se, or as such would not come within the ambit of Section 498-A IPC. It would be an illegal or immoral act, but other ingredients are to be brought home so that it would constitute a criminal offence. There is no denial of the fact that the cruelty need not be physical but a mental torture or abnormal behaviour that amounts to cruelty or harassment in a given case. It will depend upon the facts of the said case. To explicate, solely because the husband is involved in an extra-marital relationship and there is some suspicion in the mind of wife, that cannot be regarded as mental cruelty which would attract mental cruelty for satisfying the ingredients of Section 306 IPC.

From Para 17, Final nail in the coffin,

17. In the instant case, as the evidence would limpidly show, the wife developed a sense of suspicion that her husband was going to the house of Ashwathamma in Village Chelur where he got involved with Deepa, daughter of Ashwathamma. It has come on record through various witnesses that the people talked in the locality with regard to the involvement of the appellant with Deepa. It needs to be noted that Anjanamma, being not able to digest the humiliation, committed suicide. The mother and the brother of Anjanamma paved the same path. In such a situation, it is extremely difficult to hold that the prosecution has established the charge under Section 498-A IPC and the fact that the said cruelty induced the wife to commit suicide. It is manifest that the wife was guided by the rumour that aggravated her suspicion which has no boundary. The seed of suspicion planted in mind brought the eventual tragedy. But such an event will not constitute the offence or establish the guilt of the appellant-accused under Section 306 IPC.

Citations : [2017 SCC 11 176], [2017 SCC CRI 4 242], [2016 SCC ONLINE SC 1363], [2016 AIR SC 5430], [2016 SCR 11 509], [2016 CRIMES 4 184], [2017 CRI LJ 264], [2017 AIC 169 211], [2017 KLT 1 125], [2017 KCCR 1 673], [2017 ECRN 1 1]

Other Sources :

https://indiankanoon.org/doc/33506004/

https://www.casemine.com/judgement/in/5837160c53bee74f64c25ebc