Minnesota Attorney General Keith Ellison upgraded charges against police officer Derek Chauvin over the killing of George Floyd, and has filed charges against the three other officers at the scene. WGBH News' Morning Edition host Joe Mathieu spoke with Northeastern Unviersity law professor and WGBH News legal analyst Daniel Medwed about the new charges and how they could play out in court. The transcript below has been edited for clarity.

Joe Mathieu: [Are] these the new charges you thought might happen?

Daniel Medwed: Well, yes and no. The attorney general did upgrade the charge from third degree murder to second degree murder, which we discussed as a strong possibility, but they're pursuing a different theory than I envisioned. So there are two types of second degree murder in Minnesota. One is predicated on a theory of intentional murder — that Chauvin had the conscious objective to kill Floyd. And as we discussed on Tuesday, I thought that was a plausible theory, that over the eight to nine minute period during which he knelt on Floyd's neck, he formulated the intent to kill. But the second theory, felony murder, is what Attorney General Ellison is pursuing. And the idea is that Chauvin committed assault, and that assault led to death. Therefore, Chauvin should be found guilty of felony murder.

Mathieu: I'm sure none of this was by mistake. Does that make it easier to convict than the idea that you presented? I'm assuming it's much harder to convict than the initial charge.

Medwed: That's an interesting point. So on the one hand, yes, it's generally harder to convict someone on second degree murder than third degree murder. The stakes are higher [and] the jury is more skeptical and vigilant. But on the other hand, felony murder is relatively easy to convict on presupposing that you can prove guilt beyond reasonable doubt of the predicate felony, in this case, assault. And I think there's a lot of evidence of assault. So in some ways, felony murder is a shortcut because you just have to show the felony and then the death as opposed to a straightforward murder charge. So it really is a very clever and, I think, significant decision.

Mathieu: How about the other three here, Daniel? What are they charged with [and] how difficult will they be to prosecute?

Medwed: Well, they were also charged with second degree murder, as well as a lesser manslaughter charge based on an accomplice theory that they aided and abetted Chauvin in committing the murder and therefore share in the blame. Notably in Minnesota, like most other states, accomplices face the same sentencing exposure as the principal actor, which means if they're convicted of second degree murder, they could be subject to a potential 40 year sentence. But as you allude to, the three different offers have slightly different levels of culpability. Two of them, Kueng and Lane, evidently helped hold Floyd down while Chauvin was perpetrating the crime. But one of them, Lane, at least seemed to express some misgivings. At one point on tape, he asked Chauvin, "hey, shouldn't we turn him on his side?" A suggestion that Chauvin rejected, but at least points to the fact that maybe Lane had some misgivings or had some humanity. So maybe jurors will treat the two differently. And the third officer, Thao, was basically standing by, and that could pose a problem because passive behavior is usually not enough for accomplice liability — you need some active behavior. So prosecutors are going to have to show that really he was doing more than just being a passive observer, that he was basically standing sentry, that he was a guard [or] he was providing assistance.

Mathieu: Understood. Okay, good. Last question that I had for you on this: if all are charged now, are we going to see all four former officers lined up at a table being tried together, or is it one by one and then maybe they're announced together?

Medwed: Well, a couple of thoughts on that. So on the one hand, Minnesota permits joint trials for multiple defendants who commit crimes related to the "same act or occurrence." So in theory, they could all be tried together. It's more efficient, the same witnesses are going to testify [and] the same evidence is going to come into the record. But on the other hand, one or more of the alleged accomplices might want to move for what's called a severance — a separate trial — because they want to differentiate themselves from Chauvin and maybe they fear guilt by association. But conversely, and this is where it's also interesting, prosecutors might want to try Chauvin separately based on a very different concern: that any reasonable doubt generated for one of the accomplices might spill over and hinder the case against Chauvin. This is going to be fascinating to watch it unfold.