But Supt. Bob Williams, who authored an internal review of the force's work on the Pickton file, was quick to offer explanations for many of the criticisms levelled at RCMP investigators, suggesting at a public inquiry there were no major mistakes.
Williams, then an inspector working in Alberta, wrote a report in 2002 in response to a civil lawsuit filed by relatives of Pickton's victims.
The 28-page document offered a relatively positive review of the force's investigation, concluding officers acted appropriately and wouldn't do anything differently if they had to do it over again.
A decade later, Williams revised his assessment slightly, conceding there was "room for improvement."
"Do you concede that if some of those things had been changed, Pickton might have been arrested sooner?" asked commission lawyer Art Vertlieb.
"Perhaps," replied Williams.
That careful answer appears to be the closest anyone from the RCMP has come to acknowledging there were deficiencies in the way the force handled its investigation of Pickton in the late 1990s and early 2000s, first on its own in Port Coquitlam and then as part of a joint investigation with the Vancouver police.
In contrast, the Vancouver police has offered a number of apologies, including at the ongoing inquiry, and released an extensive internal report in 2010 that identified problems within the Vancouver department and the RCMP.
Vertlieb walked Williams through a list of alleged mistakes that others have suggested hampered the RCMP's investigation and allowed Pickton to kill sex workers for years until he was finally caught.
In nearly every instance, Williams said he would have done things differently if he was involved in the case, but rejected Vertlieb's characterization that officers made "mistakes."
For example, several tipsters contacted the Vancouver police and the RCMP in the late 1990s claiming an associate of Pickton's named Lynn Ellingsen told them she saw Pickton skinning a prostitute in a barn on his farm on Port Coquitlam, east of Vancouver.
The RCMP contacted Ellingsen, but she denied ever telling the story. After initially agreeing to take a polygraph test, Ellingsen changed her mind. Investigators believed her, and discounted the informants.
Williams said he would have done more to determine whether Ellingsen was telling the truth and to convince her to co-operate with police and take the lie-detector test.
"That's my opinion of what I would have done, I don't know if I would say it was a mistake or not," Williams told the inquiry. "That was the determination made by the investigative team at that particular time."
Ellingsen later became a star witness for the Crown at Pickton's trial, and told jurors about the time she walked in on Pickton killing a sex worker.
In September 1999, when investigators decided they wanted to interview Pickton, his brother Dave asked them to wait until after the rainy season. The officers agreed, and didn't interview Pickton until January 2000.
Williams said it's not what he would have done, but: "I wouldn't say it was a mistake."
There was one problem with that interview, said Williams, because officers allowed Pickton's friend, Gina Houston, to sit in and watch.
"Is that a mistake?" asked Vertlieb.
"I would say so," said Williams, who still appeared willing to give the officers the benefit of the doubt.
"If you make every effort to remove that other person but there was no other way (to conduct the interview) then perhaps you might let them, but if you ever allowed that, then you would have to set the ground rules. Personally, I wouldn't have allowed it."
In August 1999, a surveillance team followed Pickton to a meat rendering plant and watched him drop off several metal drums, but officers never got out of their vehicles to see what was in the drums. Days earlier, an informant told Vancouver police Pickton was disposing of bodies by bringing them to an unidentified rendering plant.
Williams would have had a look, but he told the inquiry not to blame the officers who didn't.
What about the disagreement between officers involved in the case about whether there were enough staff dedicated to the file?
That's just a matter of opinion, Williams said, pointing out that some members of the investigative team felt they had adequate resources.
In 2001, a corporal with the RCMP visited the Port Coquitlam farm and interviewed Pickton without telling anyone involved in the investigation or bringing another officer along.
That was surprising, acknowledged Williams, but "he obviously had a reason for going there."
Pickton wasn't arrested until 2002, when a junior officer who wasn't involved in the missing women investigation obtained a search warrant for a tip about illegal firearms. He brought members of the missing women investigation with him to the farm, where they immediately stumbled upon the butchered remains and discarded belongings of missing women, setting off a massive search of the farm.
Pickton was eventually convicted of six counts of second degree murder and sentenced to life in prison with no parole for at least 25 years.
The remains or DNA of 33 women were found on his farm, and he claimed to have killed 49.