So trustworthy as never to be suspected of wrongdoing, as in "The wife of Caesar must be above suspicion¹" (Charles Merivale, A History of the Romans under the Empire, 1850). The phrase was given further currency when it was used for the title of a very popular World War II spy film starring Joan Crawford ( Above Suspicion, 1943).

Note:

above suspicion形容某个人太值得信赖，而不需要被怀疑。最初来自1850年A History of the Romans under the Empire一书：身为凯撒妻，必须无可疑。1943年二战间谍电影《致命疑云》播出后得到广泛使用。