There are many techniques prosecutors can use to try to obtain a conviction. The strategy that is ultimately utilized is heavily determined by the facts of the case.
For example, a DUI case may hinge on the admissibility and accuracy of blood-alcohol content test results. In many instances, though, prosecutors rely on eyewitness accounts to place the defendant at the scene of the crime at the time it was committed. This can be problematic for accused individuals, but it is not, by any means, a death knell for one's criminal defense.
Often, a defense can argue that witness identification was improperly obtained. For example, if the authorities present a photo lineup containing a picture of the accused individual, there cannot be any type of marking next to the accused individual's picture that might lure the witness to identify him. Likewise, a witness may pick the defendant out of a lineup, but may not be certain that the accused was the individual he or she actually saw.
In these instances, the prosecution cannot then claim that the witness was certain that the defendant was the one who was seen. Witnesses should also be discredited, if they change their description of who they saw only after seeing a picture of the accused.
Unfortunately, eyewitness misidentification is all too common. This means that those who are confronting criminal charges should be diligent about assessing the validity and credibility of the witness. By discrediting the identification, a criminal defendant may be able to raise reasonable doubt, thereby leading to an acquittal.
In the end, though, no outcome can be guaranteed. This is why it is important to discuss these matters with an attorney who can help a defendant assess his or her situation and plan accordingly.
Source: InnocenceProject.org, "Eyewitness Misidentification," accessed on Feb. 12, 2016