CHIEF Supt Paul Howlett, of Wiltshire Police, strongly criticised Devon and Cornwall Police's handling of the investigation when he gave evidence to the inquest.
He also told it that some evidence had been inconclusive, such as the needle found in Rachel's right hand. It was capped, but tests had concluded there was no way of proving the fatal dose had come from it.
His force's investigation "has been conducted with all the rigor usually associated with a murder investigation", said Chief Supt Howlett.
"In trying to draw conclusions, it's not possible one way or another to prove whether the needle was used to inject heroin.
"It's also not possible to prove whether Rachel used that needle herself or whether is was used by a third person. It's unsatisfactory but we've followed the light as far as we can."
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