"Before God I swear I am innocent"
"Women should assert themselves more!"
"The letter asserts a free society"
He asserted that he was innocent.
他申明他是无辜的.
He asserted that his sister was innocent.
以上表达方式是正确的。
He asserted himself to be innocent.
该表达方式是错误,应改为He declared himself (to be) innocent。