In my view there is no such complication or any risk if the marriage of your friend is solemnised by the court and under the special marriage act. Both of them are major and the marriage happpened with both of there concent. There is no force or fraudulent is involved in the marriage and you are just the witness and marriage happened in the legal way so there is no need to worry as there can be no such consequences and risk.
The witness comes to the picture after the couple file a notice of intended marriage in the specified form to the marriage registrar of the district stating the intention to get married. At least one other parties to the marriage has to reside for a period of not less than 30 days immediately preceding the date on which such a notice is given. The court checks all the documents to ascertain whether they are indeed eligible to get married as per the law. It then publishes/ puts up a notice inviting objections. The time period for this is 30 days. the witness comes into the picture once no objection is received against the marriage and the bride and the groom are at the marriage registrarÕs office to sign a declaration accepting each other as their lawfully wedded husband and wife respectively. The declaration has to sign in presence of three witnesses before the registrar which is further countersigned by the registrar of marriages.
Reference: The law governing the case is the is the Special Marriages Act, 1954 (SMA) is the legislation that is used to register inter-religious and inter-caste marriages in India. It allows two individuals to solemnise their marriage through a civil contract. There are no religious formalities that need to be carried out under the Act.