Eyewitness testimony falls under the category of direct evidence because the facts that are said by the witness either prove or debunk the story. However, the validity of eyewitness evidence is not always high for which you have to be careful when to use it and for what purpose.
In a car accident, for example, an eyewitness can prove or disprove whether the driver who had the crash committed any traffic violation. Under these circumstances, eyewitness evidence is almost always reliable.
Yet, since eyewitnesses can lie, get confused, misinterpret, or doubt what they have seen, it is important for the new investigator to double check with a seasoned investigator as for the cues that can lead to what really took place. Again, it is direct testimony because it points at one fact in particular of which the witness was a participant. It is in the way that it is used and under the circumstances that the testimony is rendered that the investigator has to place special consideration to keep it valid.