Video Identification Parade Electronic Recording (VIPER) is a digital system for conducting identity parades.
 Rather than recruit a group of volunteers who resemble a suspect, police officers can retrieve a selection of pre-recorded video recordings of people unrelated to the case under investigation.
 Police officers make up a virtual parade, using clips taken from this library, and witness is then shown these, along with recordings of the current suspect.
 The system is used by many police forces across the UK.
The Glenanne gang or Glenanne group was a secret informal alliance of Ulster loyalists, mostly from Northern Ireland, who carried out shooting and bombing attacks against Catholics and nationalists during the Troubles, beginning in the 1970s.
 Most of its attacks took place in the "murder triangle" area of counties Armagh and Tyrone.
 It also launched some attacks elsewhere in Northern Ireland and in the Republic of Ireland.
 The gang included British soldiers from the Ulster Defence Regiment (UDR), police officers from the Royal Ulster Constabulary (RUC), and members of the Mid-Ulster Brigade of the Ulster Volunteer Force (UVF).
 Twenty-five British soldiers and police officers were named as purported members of the gang.
 Details about the group have come from many sources, including the affidavit of former member and RUC officer John Weir; statements by other former members; police, army and court documents; and ballistics evidence linking the same weapons to various attacks.
 Since 2003, the group's activities have also been investigated by the 2006 "Cassel Report", and three reports commissioned by Irish Supreme Court Justice Henry Barron, known as the "Barron Reports".
 A book focusing on the group's activities, "Lethal Allies: British Collusion in Ireland", was published in 2013.
 It drew on all the aforementioned sources, as well as Historical Enquiries Team investigations.
Bonnie Elizabeth Parker (October 1, 1910 – May 23, 1934) and Clyde Chestnut Barrow also known as Clyde Champion Barrow (March 24, 1909 – May 23, 1934) were American criminals who traveled the central United States with their gang during the Great Depression, robbing people and killing when cornered or confronted.
 Their exploits captured the attention of the American public during the "Public Enemy Era," between 1931 and 1935.
 Though known today for their dozen-or-so bank robberies, the duo most often preferred to rob small stores or rural gas stations.
 The gang is believed to have killed at least nine police officers and several civilians.
 The couple was eventually ambushed and killed by law officers near Sailes, Bienville Parish, Louisiana.
 Their exploits were revived and cemented in American pop folklore by Arthur Penn's 1967 film "Bonnie and Clyde".
Law enforcement in Mexico is divided between federal, state, and municipal entities.
 There are two federal police forces, 31 state police forces (and two for the federal district) and one estimate suggests over 1,600 municipal police forces.
<ref name="Economist 5/3"> </ref> There are 366 officers per 100,000 people, which equals approximately 500,000 in total, but systemic corruption is endemic and police forces are often poorly trained and underpaid.
 The average wage of a police officer is $350 per month, around that of a builder's labourer, which means that many police officers supplement their salaries with bribes.
<ref name="Economist 14/10"> </ref> As of 2012, Mexico has a police force of over 544,000 people, making it the country with the fourth largest police force in the world, just behind China, India, and the United States.
Henderson Jordan (October 11, 1896 – June 13, 1958), as sheriff of Bienville Parish in north Louisiana, was one of six law enforcement officers who on May 23, 1934, ambushed the fugitives Bonnie and Clyde in a deadly encounter on Louisiana Highway 154 between Gibsland and Sailes to the south.
On July 7, 2016, Micah Xavier Johnson ambushed and fired upon a group of police officers in Dallas, Texas, killing five officers and injuring nine others.
 Two civilians were also wounded.
 Johnson was an Army Reserve Afghan War veteran who was reportedly angry over police shootings of black men and stated that he wanted to kill white people, especially white police officers.
 The shooting happened at the end of a protest against police killings of Alton Sterling in Baton Rouge, Louisiana, and Philando Castile in Falcon Heights, Minnesota, which had occurred in the preceding days.
A law enforcement officer (LEO) or peace officer, in North American English, is a public-sector employee whose duties primarily involve the enforcement of laws.
 The phrase can include police officers, municipal law enforcement officers, special police officers, customs officers, state troopers, special agents, special investigators, border patrol officers, immigration officers, court officers, probation officers, parole officers, arson investigators, auxiliary officers, game wardens, sheriffs, constables, corrections, marshals, deputies, and Public Safety Officers (at public institutions).
 Security guards are civilians and therefore not law enforcement officers, unless they have been granted powers to enforce particular laws, such as those accredited under a Community Safety Accreditation Scheme.
 Although typically the term "law enforcement officer" refers to those government agents with police powers, prosecutors are also law enforcement officers.
The 2017 Congolese police decapitation attacks occurred on 23 March 2017 in the DR Congo.
 About 40 police officers were ambushed then decapitated.
 Six police officers were released.
 All of the surviving police spoke the Tshiluba language.
 The Kamwina Nsapu terrorist group attacked the police convoy.
Frank Jude, Jr., a.k.a. Frankie Lee Jude, Jr., (born August 14, 1978) is a Wisconsin man who was severely beaten by off-duty Milwaukee police officers in the early-morning hours of October 24, 2004.
 Following a state trial that ended with the jury acquitting the three police officers charged, a federal investigation led to plea agreements with three police officers and the indictment of five police officers, including the three who were acquitted in state court.
 Before trial, one of these five pleaded guilty.
 The federal jury acquitted one of the remaining police officers and the three police officers who were acquitted in state court were convicted in federal court.
On May 14, 2009, three Hand Grenades were thrown on Police officers in Dera Ismail Khan.
 A motorcycle rider threw a hand grenade on police emergency office.
 According to local Police Chief of city, Muhammad Iqbal, 5 police officers were wounded in first grenade's explosion three of whom were seriously hurt.
 In the next half an hour, two more grenades were lobbed on two police posts near a bus stand.
 Four police officers were injured in next two explosions.
 In all the three explosions, 9 police offers were injured.
 All injures were brought to a state–run hospital.
 Ashiq Saleem, doctor at hospital, said, "we have received eight injures, three of them are serious, all of them are police officers."
 No group have yet claimed responsibility for attacks.

Question: How many police officers did the gang which was ambushed by Henderson Jordan and his team on May 23, 1934 kill? 
Answer: nine