There are several synonyms for the phrase "bear witness against" that can be used to convey the same meaning. Some of these synonyms include testify against, give evidence against, swear against, indict, accuse, incriminate and implicate. These words all imply that someone is providing information that is working to the detriment of another person or party. When someone bears witness against another, they are essentially pointing the finger and providing evidence that could potentially lead to a guilty verdict or negative outcome. It's important to note that these synonyms are quite strong and should be used with caution in order to avoid any potential legal ramifications.