Philippine senators have set themselves as an impeachment court for the trial of Vice President Sara Duterte over corruption and other criminal allegations but they voted to send the raft of complaints back to the House of Representatives due to legal questions.

Prospects for a Senate trial of Philippine Vice President Sara Duterte were thrown into doubt late Tuesday, after the Senate voted to return the articles of impeachment to the House to ensure they aren’t in breach of the constitution.

Under the Constitution, conviction requires a two-thirds majority in the 24-member Senate — 16 votes. Conversely, Duterte needs at least nine votes to be acquitted and remain in office. A conviction would mean her immediate removal from the vice presidency and a permanent ban from holding public office.