Yes. RTI can help you in knowing the cut off marks for Haryana Police Constable Examination. An application for the same can be addressed to the designated Public Information Officer (PIO) of Haryana Staff Selection Commission (HSSC).
You can mention details relating to name of the post, Advertisement / Notification No., Date of Examination etc. in the RTI application so that the PIO can inform you regarding the cut off marks for the concerned examination / recruitment.