Do you mean not reading the plagiarism checker’s output, or the paper itself? Because the latter isn’t sufficient; you’d have to have read anything the student

Do you mean not reading the plagiarism checker’s output, or the paper itself? Because the latter isn’t sufficient; you’d have to have read anything the student might’ve (presumably found by googling), and pattern match the plagiarized text. If its not blatant/poorly inserted, there’s not really any tell.