MSPs have asked the Crown Office to clarify how it handles evidence in wildlife crime cases after the prosecution of an alleged bird of prey shooting was dropped.

RSPB Scotland said one of its cameras at Cabrach in Moray recorded evidence suggesting that a hen harrier had been illegally killed in June 2013.

The camera was monitoring the active nest of a breeding pair of hen harriers on the Cabrach Estate, but the Crown Office said last month the evidence would not be admissible in court.

Wildlife campaigner Chris Packham said he was "very angry" about the case being discontinued and accused the Crown Office of a "lack of consistency".

The prosecution service said its actions had been "entirely appropriate", having concluded RSPB investigators had entered the land and gathered evidence for the purpose of prosecution, rendering it inadmissible.

The Crown Office also defended the decision to drop a similar case from Angus on the same basis.

Now, Holyrood's Environment, Climate Change and Land Reform Committee has written to the Crown Office seeking clarification on evidence admissibility.

The letter states: "The committee has noted recent high profile instances where video evidence of alleged offences was available and not utilised, it has been suggested, on the grounds of admissibility."

Committee convener Graeme Dey said: "Our committee has today written to the Crown Office seeking clarity on the use of evidence, particularly video evidence, in helping to address crimes against Scotland's precious wildlife.

"These days, there's clearly an argument for the use of video, CCTV, or even social media to be considered when a crime against any animal is alleged to have been committed.

And, as it's often the case that poaching or killing of wildlife occurs in some of the most remote areas in Scotland, these crimes can sometimes go under the radar because there is no one around to act as a witness.

"In light of recent events, we've asked the Crown Office for information on the admissibility of evidence, including video and CCTV, whether there is any clear guidance on this, and how they interpret whether evidence is admissible or not."

A Crown Office spokesman said the organisation is " committed to the rigorous, fair and independent prosecution of crime, including wildlife and environmental crime".

He added: "The investigation of crime is subject to rules which have developed over many years and aim to strike a balance between enabling justice to be done and protecting the public from illegal or irregular invasions of their liberties.

The Crown requires to, and will, apply the law fairly and independently to the circumstances of each case.

"Discussions have taken place over a number of years between RSPB and COPFS about the admissibility of evidence obtained through the use of covert surveillance.

"The Crown has consistently made clear the limitations which the law places on the admissibility of evidence which has been obtained irregularly. The Crown will continue to have further dialogue with RSPB to explain the legal position."

Ian Thomson, head of investigations at RSPB Scotland, said: "We welcome this letter from the ECCLR Committee to the Crown Office, as it repeats many of the concerns that we have over the decision making process with regard to these recent cases.

"We have had a significant volume of correspondence regarding these issues and there has been considerable interest on social media. We look forward to the Crown Office response with interest."