Title: In the line of duty: How often are US police killed? - BBC News
Headings: In the line of duty: How often are US police killed?
In the line of duty: How often are US police killed?
How often are police killed?
Why does it fluctuate?
How do police prepare themselves?

Content: The attack, which took place at a Dallas protest over recent police shootings in Louisiana and Minnesota, is considered the deadliest day for US police in the country since the 9/11 attacks, according to records published by the National Law Enforcement Officers Memorial Fund. The gunman, 25-year-old Micah Xavier Johnson, told negotiators he was upset about police killings of black people and wanted to kill white officers. But as the nation continues a conversation on racism and police relations, Thursday's attack highlights the dangers that officers face in the line of duty. How often are police killed? So far in 2016, 56 US law enforcement officers have died in the line of duty, 26 of whom were killed by gunfire, according to data from the Officer Down Memorial Page. However, experts say annual totals can be misleading. David Harris, a University of Pittsburgh law professor, says we cannot predict how many police killings will take place through the remainder of 2016, which makes it difficult to determine if police killings are on the rise. "Trends are up and down year to year," he says. For example, 2015 marked a record low with 16 officers killed by gunfire during the first six months, which makes 2016 look particularly high in comparison, says Seth Stoughton, a former policeman and University of South Carolina law professor. However, over the last 10 years, an average of 27 officers were killed by gunfire that was not accidental during the same period, according to Mr Stoughton, citing the FBI's Law Enforcement Officers Killed and Assaulted data.