Current laws of Evidence contradict Bragg’s actions.
EXCULPATORY evidence MUST be presented.
In most states, prosecutors must present exculpatory evidence to the grand jury. In some states and in federal court they do not. I do not know whether New York requires the introduction of exculpatory evidence or not.
Even in states where prosecutors must give exculpatory evidence to the grand jury, that does not mean that they have to offer every piece of evidence that is helpful to the accused or that might be used at trial by the defense. Generally, evidence that could be used to impeach a prosecution witness as a liar does not have to be given to the grand jury, because it does not directly negate the commission of the crime.
After an indictment and arrest, the prosecutors must produce any exculpatory evidence that they have to the defense.