Yes. You can always testify about what you remember. However, it is certainly helpful to have other people testify as to what happened because an insurance adjuster might think you are motivated by self-interest in what you say. After all, it is not unusual in a crash for the drivers to point the finger at each other. Witnesses are less biased.
At Ladah Law, we always talk to our clients about what they remember. But we also seek out the testimony of other witnesses to a crash.