A campaign by Jack's mother, Sheena, led to an IPCC inquiry
A police force has apologised for its handling of an investigation into the death of a teenager.
Warwickshire Police said it "made mistakes" in the case of Jack Macleod, 17, whose body was discovered in a river in Leamington Spa in 2006.
A campaign by his mother, Sheena Macleod, led to an Independent Police Complaints Commission (IPCC) inquiry.
A man was found not guilty of killing Jack after a judge ruled there was no case to answer.
Mark Hoolichan, 21, from Wolverhampton, was cleared of manslaughter following the death of Jack, whose body was found in the River Leam.
Judge Melbourne Inman said: "There is no evidence at all as to where the deceased entered the river, in what circumstances or when.
"The reality is, anything could have happened. There is no evidence at all as to what did."
The body was discovered weeks after the engineering student had gone missing in December 2005, following a night out with Mr Hoolichan.
The body of Jack Macleod was found weeks after he went missing
An inquest into the teenager's death in 2007 was halted after witness statements and a police interview transcript were not submitted to the coroner.
The inquest has not yet resumed.
Jack's father, Ewan Macleod, told the BBC that when he called police on 4 December 2005 to report that his son had not come home, he was told to "give it a couple of hours and then give us a ring back".
A confidential report commissioned by Warwickshire Police, which has been seen by the BBC's Inside Out programme, said the time Jack went out was not recorded correctly in a second call to police.
Meanwhile, an IPCC report said that ideally CID would have been involved on the Sunday, 4 December.
The report also said the scene where Jack was last seen should have remained cordoned once "the thought had occurred" that a crime might have taken place.
In a statement to the BBC, Assistant Chief Constable Bill Holland said the IPCC supervised investigation into the complaints made by Mr and Mrs Macleod resulted in a number of complaints being substantiated.
ACC Holland added he was "very sorry" for distress caused to the family.
He said: "Whilst nothing we could have done would have saved Jack's life, the mistakes that were made meant that the investigation into his death was more protracted than it should have been.
Det Insp Bob Bradbury said he asked for more staff, but was denied
"We got some things wrong then, we have recognised and accepted this, and made significant changes to address these issues."
Jack's family have made dozens of complaints.
Sheena Macleod told the BBC: "We feel that as Jack's parents, we've parented him through to this apology which was due him and us.
"We were and still are his advocate from the grave and his voice and we got him that apology."
Det Insp Bob Bradbury, who led the original investigation and has since retired, told Inside Out: "I believe that I did everything in my power with the resources that I had at my disposal [and] that I ran a correct and valid investigation into the disappearance of Jack Macleod.
"I did ask for more staff. Denied. I did ask for trained staff. Denied. I did ask to be written off for this inquiry. That was denied.
"I had my day-to-day job of running Warwick district CID to do alongside this inquiry. Under normal circumstances I would've been written off to solely do this inquiry."
The IPCC report said "it is commented upon... that were he still a serving officer it is likely that DI Bradbury would face a misconduct hearing".
Mrs Macleod said: "He was working for Warwickshire Police force, but at the end of the day Warwickshire Police force isn't about one person."
On behalf of Mr Hoolichan, Gregory Burke, of Rogers & Co Solicitors, said: "We fully appreciate that the disappearance of Jack MacLeod raised suspicions that needed to be fully investigated.
"However, we agree with the findings of subsequent reviews in that the initial hypothesis that Jack MacLeod's death was as a result of a sinister act on behalf of Mark Hoolichan was not borne out by the evidence that the investigation revealed."
At his trial a submission by the defence of no case to answer was upheld by the trial judge, who directed the jury to return verdicts of not guilty, Mr Burke added.
Inside Out is broadcast on BBC One in the West Midlands at 1930 GMT on Monday, 1 March.
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