MICHEL MARTIN, HOST:

Now we're going to revisit a story that shocked many people. On Monday, the murder trial against former police officer Michael Slager ended in a mistrial when the jury reported it could not reach a unanimous verdict. The case drew national attention in part because of cellphone video footage showing Slager, who is white, shooting Walter Scott, an African-American man who was unarmed and was running away.

We wanted to know why so few of the recent cases involving police killings, particularly those involving unarmed black men, seem to result in convictions. So we turned to Seth Stoughton. He's a law professor at the University of South Carolina. He previously served as a police officer in Florida. And I started our conversation by asking why the jury in this case seemed to have trouble coming to a conclusion.

SETH STOUGHTON: The prosecutor's job is to establish guilt beyond a reasonable doubt. We had really compelling video evidence, but the video picked up partway through the encounter between the officer and Mr. Scott. So the defense strategy was to emphasize the series of events that occurred at the very beginning and then before the video itself.

MARTIN: Is the perception accurate that it is very difficult to secure convictions in these cases, and if so, why might that be?

STOUGHTON: Part of what makes these cases difficult is jurors being asked to decide whether an officer who uses force as a regular part of their job used it criminally in this case. And jurors can be very reluctant to second-guess officers and particularly officers' use of force decisions.

MARTIN: Is race a factor here?

STOUGHTON: In the context of police use of force cases, a jury or a prosecutor or a society more generally may be prone to viewing the actions of a black suspect as more threatening than the actions of a white suspect, even though we're not aware of it. So is there implicit bias, or is there the potential for that implicit bias to play into the prosecution of police officers? Absolutely, there is at the prosecutorial level, at the level of the jury and at the level of how we as society expect officers to behave with different subjects.

MARTIN: It cannot be a good thing that people view the criminal justice system so differently. As we've seen in surveys, for example, white Americans tend to have a great deal of confidence in the criminal justice system and in the police as a part of that. African-Americans, the surveys tell us, have far less confidence in the criminal justice system more broadly and police in particular. Is that a problem, and is that overcomeable (ph)?

STOUGHTON: Yes, it's absolutely a problem. Can it be dealt with? I am alternatively optimistic and pessimistic about this. I'm optimistic because I see police agencies across the country doing some really good things, trying to address root causes of distrust. And then I'm pessimistic because this is not new.

Policing in this country has gotten significantly better, but it hasn't always gotten better in the right ways. And it still has significantly farther to go. Whether or not it will ever get there, I don't know. I suppose my answer to that question depends on my mood. And in the aftermath of a hung jury, I'm not feeling particularly optimistic today.

MARTIN: That's Seth Stoughton. He is a professor of law at the University of South Carolina, where his scholarship focuses on police procedure. He also teaches criminal and criminal procedure. He was kind enough to join us from South Carolina Public Radio, which is in Columbia. Professor Stoughton, thank you so much for speaking with us.

STOUGHTON: Thank you very much for having me. Transcript provided by NPR, Copyright NPR.