Dear Shubhi, Yes, you can. Petitions like habeas corpus are most of the time files by the next friends or relatives of the detained. And courts have already relaxed the locus standi to file a PIL. Wherever you see gross injustice or violation of rights you can file petitions. Declare that you are writing on behalf of another person if it is appropriate, such as in a letter to the court. If it is a letter going out under the other person’s name you don’t have to state that she didn’t write it herself. In the case of physical injury or language problems indicate the reason.