Why do jurors tweet during trials? A law professor is writing a book about the impact of social media in the courtroom.

Judges may instruct jurors to refrain from tweeting during trials, but the explosion of social media has made it harder to guarantee an impartial jury, according to a University of Dayton law professor who is writing a book on the phenomenon.

"You see more and more instances where people are researching details about the case or posting comments about the trial. In one sexual assault case in England, a juror held a poll with Facebook friends about whether she should vote guilty or not guilty. A judge in Arkansas overturned a death penalty case because one juror wouldn't stop tweeting," said Thaddeus Hoffmeister, author of Social Media in the Courtroom: A New Era for Social Justice, due to be published later this year.

In the upcoming high-profile George Zimmerman trial, the judge is taking the rare step of sequestering the jurors to make sure they don't tap into their social media accounts or read articles on the Internet.

"The biggest problem is that jurors are relying on information that's not presented in court," said Hoffmeister, pointing out that some jurors will download Google Earth to view the crime scene. "Everyone is an expert for a minute or two on Google."

Hoffmeister will discuss ways to reduce juror misconduct in the age of social media with federal prosecutors and defense attorneys at the 39th Annual Federal Law Seminar July 25-26 at Miami University.

He recommends that judges and lawyers take these steps to address the growing problem of jurors pulling out their smart phones during jury duty:

• Allow jurors to ask questions of the witnesses. "They can even write their questions on a piece of paper and hand it to the judge. We're seeing a push for this."

• Improve instructions to the jurors. "Treat jurors like equal partners, not children."

• Penalize them. "I'm not a big proponent of this, but courts are taking a harder stance. They're giving jail time or a high fine when they catch jurors using social media inappropriately."

• Investigate and monitor jurors. "This helps level the playing field and allows attorneys to verify (in the selection process) if they're telling the truth. On the other hand, jurors argue that they're forced to be here and didn't ask to be investigated. They're not on trial."

Hoffmeister, who blogs about juries and teaches a course in social media and criminal law, is regularly sought out by The Wall Street Journal, Washington Post, Los Angeles Times, Chicago Tribune and other national media outlets for his views. He recently wrote a chapter, "The Impact of Social Media on Criminal Law," for the soon-to-be-published book, The Practitioners' Guide on Social Media Use.

"If you're a digital native, born and raised with the Internet, your answer to everything is, 'I'll Google it.' I didn't realize how big an issue this had become until I started blogging about juries. I'm constantly updating the syllabus for my class. There's nothing in my syllabus before 2010."