How severe was case JB296775? Give the index code for severity.
index code refers to iucr_no; case JB296775 refers to case_number = 'JB296775'
SELECT T2.iucr_no FROM Crime AS T1 INNER JOIN IUCR AS T2 ON T1.iucr_no = T2.iucr_no WHERE T1.case_number = 'JB296775'