Transaction rollback when multiple threads are inserting records into table because of trigger

Hi All ,I have two tables called ECASE and PROJECTIn the ECASE table there is trigger to get the max value of case_id column in ecase based on project and increment one to that case_id value and insert into ecase table .When we insert a new record to the ECASE table this trigger calls and insert the case_id column value.When i run with multiple threads , the transaction is rolled back because of trigger . The reason is , on the project table the lock is happening while getting the max value of case_id column based on project. I need to prevent the deadlock . Can any one help me out