Can the degree of a charge be changed after pretrial by the prosecution?

Absolutely charges can be changed or attempted to be changed by the prosecution but understand it is never as cleanly done as you see on television in a one hour show. The bottom line is prosecutor's are under certain guidelines of what they can bring as charges and if there is no proof (provided by or obtained through the police, investigator or other source), then a prosecutor may be forced to drop charges altogether or lower them to less serious crimes.  Every crime (whether a misdemeanor or felony and the various classes of either ) has certain elements that must be met to meet the burden by the prosecution of beyond a reasonable doubt. If the prosecutor believes he or she can find the defendant's actions meet all of the elements of a more serious crime, then that is what the prosecutor will move forward with and also provide the lesser crimes as a back up. At some point, when the judgment is rendered, and dependant upon the crimes alleged, one or both may have been committed. New evidence brought to light in testimony or before trial can sway what remains as a charge or whether the prosecution has to go back to the table with additional charges.