Trigger Stacking Leading to Canine Fatal Aggression - WARNING DISTURBING CONTENT.


Jedi Master
There are a number of incidents in this article that led to a trusted family pet re-directing aggression to his owner, and killing her in the process.

The behaviourist giving evidence has delivered a comprehensive view of the situation despite the horror of the outcome of the dogs aggression.

It's also a good reminder that if we, as pet owners, are going through traumatic experiences, then the impact of those experiences on our pets and additional training or behavioural management should be considered. The owner in this story had suffered enough that she didn't feel mentally or emotionally capable of doing her work, yet the dog was expected to maintain it's previous status as a trusted family pet despite having successfully defended the owner in a home invasion.

The behaviourist also raises another important point - frustration increases drive - unfortunately in this instance, the drive that was being increased was defence drive, known as a very unstable drive to work with because it's fear based. This also highlights the importance of good training and leadership practices with dogs prior to issues like this coming up.

Not all dogs will become aggressive under such circumstances, some will just develop more fears or lowered fear thresholds and become nervous wrecks or shut down. Or for those with firmer temperaments these experiences may just wash off like water off a ducks back. So getting a good handle on the dogs genetic temperament should be foundational to any training program.
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The Living Force
FOTCM Member
That's a very sad tragic case. And I don't think it is typical nor does the behavioral specialist.

Crosby understands that his and the coroner’s findings may be difficult for some worried members of the Canberra community to accept.
“I've seen an awful lot, more than just about anyone else, but they are very unusual occurrences. In all the cases I've been involved in there have been an accumulation of factors and if anything had gone differently, it probably wouldn't have turned out that way.

“We just have to accept that your normal pet dog doesn't kill somebody.”
It is a good example of "expect attack" and" Transmarginal Inhibition too I think.

The dog looks like a possible Pit Bull mix. My son had one that was very sweet and affectionate. I always watched her around strangers or children though. She later died from possible Cerebellar Cortical Disintegration. I am not 100% sure it was that but she did not become aggressive she just died. My son has not had the heart to get another dog since.

The details of the story do indicate the dog was hit on the head with a baseball bat in one incident too. It's is a very sad tragedy to keep in mind or like you titled it Disturbing Content.


Jedi Master
Yeah, it's heart breaking when they die. My dear old recently departed girl's breeder has another litter at the moment, and I don't think I'm ready just yet.

I hadn't heard of CCD before. It seems to have some symptoms in common with idiopathic vestibular disease.

I'm on a pro-dog trainers forum where another trainer/behaviourist had this to say about the dog in the opening post:

I met this dog a couple of times, definitely a defensive no nonsense dog that would not have hesitated to spark.
That's the problem with defence drive - it can become hair trigger reactions and there's little by way of impulse control.

When I was studying, the organisation that I studied with had a board and train kennel. There was a German Shepherd come in for aggression issues. In this dogs case his owners had attempted to train him to guard. But they had no idea about the different drives and they inadvertently trained this dog in defence drive. I'm not sure if they used google trainer for guarding, but some of the methods used by idiots that build defence drive are pretty horrible. Upshot was that he would never be stable enough to be in a domestic situation again.

When we first observed him, he was in a kennel run behind a double chain link fence. One of our instructors went between the two fences to demonstrate how unstable this dog was. He approached the inner fence in a non threatening manner - side on, no direct eye contact. He squatted down outside the fence and slowly reached into his treat pouch and handed some treats through the fence - still without making eye contact, and side on to the fence. Then without warning, he simply held his hand out in front of himself, palm down. This was enough to send the dog into a defensive fury. This dog had become so hair triggered in his response that if he could not reliably predict that an action was going to bring him reward, then it was immediately deemed to be a threat. He just kept hitting the fence with force, snapping, snarling and spraying saliva.

They were going to work with this dog to bring his confidence back up. I saw him again 6 months later, this time in an on leash demonstration. That morning our instructor picked us up from our accommodation and even though it was quite warm, he had a few layers of clothes on. I asked him if he was unwell and he replied 'No, I'm handling Zac today and he doesn't like me.'

There was only one girl that Zac trusted enough to put a lead on him, and they used a 'soft handover'. It was a long 10m lead because a defence drive dog will often just opt to move away if it feels it has a choice rather than attack if it's triggered. So the girl walked him out into a big yard and as Zac forged ahead on the lead, my instructor pealed in and walked next to the girl for a few paces before she handed the lead over and then pealed away while Zac was still walking ahead.

Over the course of 6 months they'd built Zac's confidence up to the level where he would hold a drop stay while another trainer swung a stick at him, pretending to be a threat - that was massive! But, to relieve the stress loading, they still had to let Zac get a bite in. So the trainer that was swinging the stick also had a bite sleeve on. Zac held the stay though until my instructor gave him the command to bite. Then the trainer would take the bite on the sleeve, put a bit of agitation into it to give the Zac the impression he was fighting, and then he'd totally let the sleeve go so that the Zac got the impression that he'd been triumphant in the fight - he'd trot off with his head high and the bite sleeve in his mouth. The whole reason that they kept Zac and kept working with him was so that we students could learn to see the body language differences between defensive aggression and other types.

Zac did become more stable over time, but even so it was best that he stayed living with professionals because they knew how to control his environment to protect the trust he was gaining and there was little by way of unexpected events happening around him.


The Living Force
FOTCM Member
Zac did become more stable over time, but even so it was best that he stayed living with professionals because they knew how to control his environment to protect the trust he was gaining and there was little by way of unexpected events happening around him.
Wow, that's a very sobering story. It reminds me of Inside the Criminal Mind by Samenow and this thread. Even humans are very difficult to "retrain" or reprogram.
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