I just wonder, if her office is going to charge the person with first-degree murder, then why withhold the announcement while announcing the press conference. Just announce the charges and file them as soon as possible.
However, there's one main reason to hold a press conference, and that's if the top charge is not being applied. Then you'll have to explain your office's reasoning. And if it's a negative thing that you're announcing, you want to be there to take the questions immediately and face-to-face.
Perhaps, she'll announce an initiative to make killing a police officer one of the felonies for which first-degree felony murder is applied. Right now, it's a limited bunch of felonies, such as armed robbery or rape, and the idea is this, even if one does not intend to kill someone, if someone dies during the commission of a felony, it's the same as premeditated murder.
So the press conference could be used to highlight a shortcoming in the law.
Otherwise, if you're announcing a top charge, are you just using the opportunity for some face time? I hope not, not with the death of a police officer. Let the wheels turn and don't make it about you, unless there's something tricky that needs explaining.
When Worthy announced charges against disgraced ex-Detroit Mayor Kwame Kilpatrick, she held a press conference, and that was necessary, for it was a political event and she owed it to the city and surrounding area to explain what she had and why she was doing what she did.
Whatever happens, I'm interested in what Worthy has to say about this current case. Nothing in Detroit will ever get fixed if police officers are getting killed or if teachers lack support to do their jobs. No one 'moves forward' if the basics are not covered.