According to the Baltimore Sun, factual guilt concerns whether or not someone committed a crime as a matter of historical, factual record, while legal guilt is entirely dependent on the decision of the jury. The Legal Information Institute of the Cornell University Law School states that reasonable doubt is any doubt that is sufficient for a jury to acquit a defendant on grounds of insufficient evidence.
The Baltimore Sun article explains that factual guilt may correspond to legal guilt, but the two are not conceptually identical. A person might have committed a crime but if the jury does not find her guilty, she is not legally guilty. A person who is not factually guilty can be legally guilty if the jury decides that is the case. Once a jury finds a defendant legally not guilty, that person cannot undergo another trial on the same charges, as a second trial is prohibited by double jeopardy laws. The American legal system does not ask jurors to pronounce whether the defendant is factually guilty or not guilty. As a result, the jury's pronouncement of guilt is a response to the question of whether or not it believed that the prosecution provided proof of the defendant's guilt, and whether or not the evidence proved the defendant's guilt beyond any reasonable doubt.