A boy’s hooded top was discarded in a skip despite being recovered on a shoreline days after the body of Alesha MacPhail was found.
A murder trial heard that a dog walker contacted police on 6 July last year after spotting the youth XL garment on the Isle of Bute.
It was put in an evidence bag then dumped in a skip behind Rothesay Police Station by a police sergeant.
A 16-year-old denies abducting, raping and murdering six-year-old Alesha.
He cannot be named because he is under the age of 18.
It is alleged that Alesha was taken from the home her grandparents shared with her father.
Her body was discovered in a wooded area on 2 July last year.
The jury previously heard that Alesha suffered 117 injuries, although some could have been caused by vegetation in the area where she was found.
She died from significant pressure being applied to her face and neck.
On Friday the High Court in Glasgow was told a black Nike hooded top was initially found by Zareya MacGillivray.
She contacted police and it was recovered by Sgt Anthony Hannah, using gloves and an evidence bag.
But the jury heard the officer later put it in the bin after consulting with a colleague.
Sgt Hannah said the discovery came after the arrest of the 16-year-old suspect.
He added: “At that time we had no information that there was anything outstanding from the inquiry.”
Under cross examination by Brian McConnachie QC, for the accused, he denied his actions had been “reckless”.
Sgt Hannah told the court the top was found about half a mile outside the designated parameters set by search advisers for the investigation.
It was removed from the skip when the inquiry team was made aware of it.
The court also heard about a knife that was found on the shore opposite Alesha’s grandparents’ house.
Coastguard volunteer Peter Morrison, 39, from Rothesay, told the court he was called out to carry out a shoreline search at 06:55.
He said that opposite the house where Alesha had been staying, he found “what looked like a kitchen knife”.
Mr Morrison said he did not touch the knife – which he believed had been in the sea and left onshore by the receding tide – but noted its location before continuing to search for Alesha.
He later told police who cordoned off the area.
The accused teenager has also been charged with attempting to hide evidence.
He has claimed it was Toni McLachlan, the partner of Alesha’s father, who killed the child.
During her evidence to the court on Wednesday, Ms McLachlan insisted she had nothing to do with Alesha’s death, telling jurors: “I loved her to pieces.”
The trial, before Lord Matthews, continues.
Why is the BBC not naming the accused?
It is illegal in Scotland to publish the name, address, school or any other information which could identify anyone under the age of 18 who is the accused, victim or witness in a criminal case
This law applies to social media as well as to websites, newspapers and TV and radio programmes.
However, the name of victims who have died can be published – so the BBC and other outlets are able to identify Alesha MacPhail.
How can an accused blame someone else for the crime?
Ahead of their trial, the accused can lodge a special defence such as self-defence (they were defending themselves from attack), alibi (they were somewhere else when the crime was committed) and mental disorder (the accused is not responsible for their actions because they were suffering from a psychiatric condition).
In this case, the accused has lodged a special defence of incrimination, which means he has claimed that someone else (Toni McLachlan) was responsible.
However, the Crown must still prove the guilt of the accused beyond reasonable doubt. There is no onus on the accused to prove their special defence is true, and he or she can still be acquitted even if the jury does not believe their special defence.