A University of Canterbury criminologist believes whoever is responsible for the slaughter of more than 215 sheep in Ngapara is either young and ''thrill-killing'' or an ''adult who's demented''.
Prof Greg Newbold, who has done extensive research on the criminal use of firearms in New Zealand, described the crimes as ''sick'', ''sad'' and ''strange''.
On the face of it, it did not look like a motiveless crime - ''it looks like a vendetta'', he said.
But targeting more than one farm suggested otherwise and it could likely be the work of a young person, or persons, killing ''for the thrill of it'', he said.
''Whoever is doing it, they would have to be bloody young and bloody stupid,'' he said.
''Seeing a whole lot of [sheep] die, they must know they are causing immense anguish to owners.''
In a small community such as Ngapara it would be difficult to execute such a crime without someone finding out, he said.
Prof Newbold guessed the culprit or culprits did not hold a firearms licence, instead illegally possessing the weapon, or weapons.
Targeting properties at weekends suggested they worked during the week and he also believed the crimes could be alcohol-fuelled.
In the first attack, on Peter and Janine Stackhouse's sheep, more than 200 shots would have been fired to kill about 195 sheep.
''That's a hell of a lot of shots fired ... without being heard,'' Prof Newbold said.
Determining the type of weapon and ammunition used would be of critical importance to the investigation, he said.
''Whether they were using solids or expanding projectiles,'' he said.
Expanding projectiles could be bought from a sports shop, while full metal jacket solids would be much more difficult to obtain.
''There wouldn't be many people who would buy them other than people who belong to gun clubs,'' he said.
If it was solid ammunition, the culprits were likely to be using a military-style semiautomatic (MSSA) firearm.
A specific endorsement from the police is needed to possess an MSSA firearm.
''It's not too hard to start narrowing things down,'' Prof Newbold said.
The culprits had been ''smart enough'' to get rid of casings, he said.
''If they are doing that, it's probably not an MSSA - they spew casings out all over the place - [whereas] bolt action [guns] get the casings every time you work the bolt.'' he said.
''You wonder whether they are saving the cases ... [they] could be saving the casings in order to do reloads. In which case they wouldn't have to go to the shop, but the original [ammunition] would have to have been bought.''
People who were making their own ammunition would have the necessary equipment in large amounts, he said.
''If they are making their own, someone is going to know about it.''
Prof Newbold poured cold water on concerns the culprits could be capable of much worse crimes.
''I wouldn't be too worried about that,'' Prof Newbold said.
''[The culprits are] stupid, young and probably pretty thick. They're going to get caught and everything points to it being an easy crime to solve.''
That a smaller number of sheep were killed on John and Wendy Dodd's farm could be an indication the culprits were running out of ammunition.
''If they continue, I would say they have made their own ammunition. They won't be able to go into a shop and buy a whole lot and not be noticed.''
If they were ''thrill-killers'' they would soon ''get over it'', he said.
''It will be interesting to see what happens.''
Police inquiries into the killing of the sheep were ongoing, as they continued to work through information received from the public, a spokeswoman said.
Profile
Greg Newbold's profile indicates the Ngapara offender is possibly:
• Young
• Thrill-seeking
• Not very bright
• Does not hold a firearms licence
• Employed
• Not a risk to others
• Can make their own ammunition
