USA Today: when citizens film police, it shouldn't be a crime.

USA Today:
In one-party consent states if a citizen video & audiotapes a police officer. State laws allow the DA to charge people with illegal wiretapping. It is an abuse of prosecutorial authority and a misinterpretation of state law to charge people with illegal wiretapping. It's typical of the attitude of too many prosecutors and police toward people who record their encounters with law enforcement and are usually completely within their rights to do so.

Websites that monitor these cases have posted stories from around the country of police ordering people to stop videotaping or photographing them, sometimes violently. Most of the time, the police apparently either don't understand the law or are deliberately misstating it to bully people into putting away their cameras or cellphones.

Only in Massachusetts and Illinois is it explicitly illegal to make an audio recording of people without their consent, so officials there can prosecute those who tape police encounters. Ten other states, including Maryland, have "two-party consent" laws that require both (or all) people being audiotaped to approve, but the statutes apply to "private" conversations, such as a phone call. Generally, courts and prosecutors conclude that an officer arresting someone in a public place has no expectation of privacy.

Link:
http://www.usatoday.com/news/opinion/editorials/2010-07-15-editorial15_ST_N.htm