Slang idioms

"It turns out that Mrs. Banks committed the crime. Apparently, she and the victim had been in a relationship together in high school. He became disenfranchised with her after she repeatedly stalked him at school and he. subsequently, ended the relationship. Years later, he got married but she, apparently, held on to some kind of twisted hope that they would get back together. Once she found him unwilling to leave his wife, she shot him. I guess that old ..... die hard," Police Inspector Jones said to the chief.