In 1983, Sri Lankan army troop was patrolling in Jaffna palace. They were ambushed by LTTE and 13 were killed and 2 were severely injured by LTTE. This lead to black July and this seems as beginning of civil wars. Since starting of this civil war, more than 80 k people were killed and more than 1 million made homeless.
A same foreign policy can be formed and applied differently for neighbouring countries and other countries. It makes a strategical impact on developing relationship with neighbouring countries. By this the decision making in any issue relating to neighbouring country and other countries can be different.
At a required situation, every country can make a decision at considering three aspects Political, Ethical, Strategical. Even though UN resolutions were supported by India in the past, the idea of involvement of the International Independent body in investigating the Sri Lankan human right issue was oppose by India. International independent body although appears to be completely independent from any country, it might be interfered by other countries, this is also one of the reasons India not supporting UN resolution idea. The resolution passed with 23 votes for 12 against and 12 abstentions. This Idea was abstained by India because India believed that adopting an intrusive approach undermining national sovereignty and institutions is counterproductive.
In the past America, Iran and Iraq violated many rules and regulations but no independent third party body was introduced into the affair to investigate through it, but this time a third party was involved instead of supporting its own body. The incident involving 80000 people dead and more than 1 lakh homeless is far crossed the obstruction of human rights. Human rights have no state/boundary, this is universal. So, as per all this, Indian decision seems to be wrong in the ethical sense. If India supports UN decision of introducing a third party investigation body in Sri Lanka, then India itself might get investigated for Kashmir and terrorism by International independent body.
Sri Lankan issue was treated as Tamil Nadu issue because most of them were immigrants from Tamil Nadu. If the resolution was not supported, then it might lead to government issues in Tamil Nadu.
If India neutralizes the UN decision about investigation in Sri Lanka, Our relationship with neighbour country would differ and it becomes strong. As the relationship between India and Sri Lanka is disturbed, strategically it advances the other countries to develop relationships weakening our strength in the neighbourhood. China already digs its root in Sri Lanka, so at strategical solution for a problem should also be considered. India should consider also decision considering ethical sense giving the right of justice for the victims of the issue. India should have talked to authorities in helping to develop a own body to investigate the issue and prevail justice.
The abstention gives India greater flexibility with Sri Lanka, greater ability to push for charges that Sri Lankan Govt. needs to undertake. It has taken some steps in the last year like holding provincial council elections in the north which did not happen because of the HRC vote, but because of intensive Indian diplomacy.