Question: Mark Prothero was co-counsel for the man who was convicted of how many murders?

Context paragraphs:
Gary Ridgway: Gary Leon Ridgway (born February 18, 1949) is an American serial killer known as the Green River Killer.  He was initially convicted of 48 separate murders and is presumed to be responsible for more than 90.  As part of his plea bargain, an additional conviction was added, bringing the total number of convictions to 49, making him the most prolific American serial killer in history according to confirmed murders.  He murdered numerous women and girls in Washington State during the 1980s and 1990s.

Mark Prothero: Mark Wayne Prothero (1956 – April 19, 2014) was an American attorney in Kent, Washington.  He was best known for serving as defense co-counsel for the Green River Killer, serial killer Gary Ridgway from 2001 to 2003.

Arthur Allan Thomas: Arthur Allan Thomas (born 2 January 1938) is a New Zealand man who was granted a Royal Pardon and compensation after being wrongfully convicted and imprisoned for murder.  Thomas was convicted in 1971 of the murders of Harvey and Jeannette Crewe, who had been killed in June 1970 in Pukekawa, south of Auckland.  Thomas, who farmed a property in the same district as the Crewes, was again convicted of their murders after his conviction was quashed on appeal, but he was released in December 1979 after being pardoned and awarded NZ$950,000 in compensation for his 9 years in prison and loss of the use of the farm.

Atlanta murders of 1979–81: The Atlanta murders of 1979–1981, sometimes called the Atlanta Child Murders (although several of the purported victims were adults), were a series of murders committed in the American city of Atlanta, Georgia, from the middle of 1979 until May 1981.  Over the two-year period, at least 28 African-American children, adolescents and adults were killed.  Wayne Williams, an Atlanta native who was 23 years old at the time of the last murder, was arrested for and convicted of two of the adult murders, and sentenced to two consecutive life terms.  Police subsequently have attributed a number of the child murders to Williams and closed the cases, although he has not been tried or convicted in any of those cases.

Frank Abbandando: Frank Abbandando (July 11, 1910 – February 19, 1942), nicknamed "The Dasher", was a New York City contract killer who committed many murders as part of the infamous Murder, Inc. gang.

VVT (gang): VVT is a Tamil gang in Toronto believed to be named after the Sri Lankan town of Valvettithurai.  It was founded in the early 1990s by Tamil immigrants.  The VVT had a strong presence in the west end of Toronto (in particular in Etobicoke and certain areas in Old Toronto and East York) and was regarded as being very business savvy and motivated by the profits of crime.  The VVT were considered to be highly organized with members ranging in age from their early teenage years to men in their 30s, with members from to 100-500 strong.  In the mid to late 1990s and early 2000s the VVT had an ongoing war with another powerful Tamil gang called the AK Kannan based out of Scarborough.  There was a brief truce in 1998 after community members brokered a peace deal in a Richmond Hill Hindu temple; however, a murder a year later renewed the fighting.  VVT is behind many murders in the 1990s.

Chilobwe murders: The Chilobwe murders were a series of murders, numbering at least thirty killings, which took place over several months starting in November 1968 in the suburbs of Blantyre, Malawi, particularly in Chilobwe.  A number of rumours grew up around these murders, and many blamed them on the South African Government which, according to various popular accounts, wanted repayment of loans it had given to the Malawi Government, either in human blood or by the enslavement of Malawians to work in South Africa.  These rumours were politically damaging to the government of Hastings Banda, which cultivated friendly relations with South Africa's white minority government, and he treated the murders as a serious issue requiring urgent resolution.  The murders were never fully solved.  Several men were arrested in connection with the murders in 1969, but acquitted for lack of evidence.  This caused popular outrage at the criminal justice system which, at that time, was still based on English law and practice.  In 1970 another man, Walla Kawisa, made several confessions admitting to some of the murders.  He was condemned to death and probably executed in May 1972.  It is unlikely that the murders were the work of a single individual, and various theories have been proposed, some linking them to opposition to Banda.  Banda himself blamed the murders on ex-ministers involved in the Cabinet Crisis of 1964, and removed Gomile Kumtumanji, a Member of Parliament cabinet minister for the Southern Region from office and had him tried for treason, allegedly for complicity in them.

Malexander murders: The Malexander murders (Swedish: "Malexandermorden" ) were the murders of two police officers, Robert Karlström and Olov Borén, at Malexander, Sweden on 28 May 1999.  The murders were committed after a bank robbery in Kisa earlier that day.  Three men were convicted of the crimes, Tony Olsson, Andreas Axelsson and former mercenary Jackie Arklöv.  The murders in Malexander were among the most high-profile cases in Sweden.  The three perpetrators were active neo-nazis and the robbery spree before the murders was committed as part of their plan to collect money to fund and create a "revolutionary" nazi organization.

Frank Schweihs: Francis John Schweihs (February 7, 1932 – July 23, 2008), aka "Frank the German", was an American gangster, who worked for The Outfit, the organized crime family of Chicago.  At the time of his death, federal prosecutors planned to indict him for numerous crimes, including murder.  It is believed he had participated in, or had knowledge of, many murders going back decades, including brothers Anthony "Tony the Ant" Spilotro and Michael Spilotro, Allen Dorfman of the Teamsters Union, a disgraced Chicago cop, Outfit associate and informant Dick Cain, Outfit boss Salvatore "Sam," "Mooney" Giancana, loanshark Sam "Mad Sam" DeStefano, Outfit hitman Charles "Chuckie" Nicoletti and others.

Chester Turner: Chester Dewayne Turner (born November 5, 1966) is an American convicted serial killer.  On April 30, 2007, he was convicted of the murders of 10 women in Los Angeles, and was also found guilty in the death of the unborn child of one of his victims.  He was convicted of 4 additional murders on June 19, 2014.  Prosecutors have called Turner "one of the most prolific serial killers in the city’s history".  On July 10, 2007, Turner was sentenced to death for the 11 murders he was originally convicted of committing.  On June 26, 2014, Turner was sentenced to death a second time for the 4 additional murders.

Supporting paragraphs: Mark Prothero Gary Ridgway
Answer: 48