Then came the serious wounding of his younger brother, Jason, who followed him into the force. The rookie cop was off-duty with colleague Constable Peter Forsyth when they were approached by a teen drug dealer in inner-Sydney in 1998. As they tried to detain him, the teen stabbed Jason twice in the stomach and fatally knifed Forsyth.  

Nothing, however, could prepare Semple for “the worst crime scene” he encountered in 2003 in Maclean on the NSW north coast.

“Imagine a bloke in a house that tells another to lie on the floor and puts a shotgun to his head and executes him, then drags him through the house into another room – so from the front to the back of the place, there was nothing that wasn’t affected,” he says.

“It was an isolated house in a cane field and what was different was that I had to clear it on my own. I knew something was bad but I didn’t know if anyone needed help and I had to take my gun out and know that I had to face a threat. It started the process of flooding my system with adrenalin and as I went through the house clearing each room of danger I was so flooded with adrenalin that by the time I go to the victim the adrenalin had scrambled the way my brain processed those images.”

 Semple soon began having nightmares he chose to ignore.

“I knew it wasn’t right but no one dies of a nightmare, so it was just like ‘harden up’ and go to work and put up with it. Because everyone I knew in the office who had put up their hand for mental health reasons had been discharged, and there was no way I wanted that.”

For almost another decade, Semple soldiered on, self-medicating with alcohol and more adrenalin as a coping strategy.

Based in Grafton, his focus was high-risk drug and bikie investigations.

“I would go to work and if I was feeling down and flat, organise a drug raid and go and knock a door down and come back feeling great – I needed that buzz and adrenalin . . . it was like a drug addiction,” he says without flinching.

“But everything that goes up must come down. Back home the adrenalin would flush through me and I came to be in a depressed state that I associated with my family life. I had unrealistic views of how happy I was at home.”

Semple later learnt his insomnia and hyper-vigilance – including grabbing his weapon at home and clearing the house of danger if he heard a noise – were symptoms of Post Traumatic Stress Disorder. 

He was an angry, irritable man, increasingly detached from the world: “I didn’t feel plugged in, you know all those nice emotions like love – I couldn’t tap into them.”

Semple had just wrapped up two high-pressure jobs – the investigation of former Knights prop Danny Wicks for drug trafficking and the arrest of more than 20 bikies on the north coast – when he crumbled.

“A little bit of stress is good for you to get you motivated but it releases adrenalin and also cortisol, and when that is maintained for high levels at length it can be neuro-toxic and causes damage,” he says.

“After the Wicks job I didn’t get a break . . . I put together the [bikie] strike force and went for nine months without a break, thousands of phone calls we had to listen to, undercover operatives, drug raids and getting into physical fights with them. The difference is, they know where we live, where our wives work, where our kids went to school and they let us know.”

On the day of the raids that nabbed almost an entire chapter of the gang, Semple’s mood began to plummet. He went to see a psychologist and she said he showed major signs of stress and major depression.

“I went home and I was telling my wife about it and I just collapsed on the kitchen bench and couldn’t stop crying,” he says of the moment in mid 2012.

Discharged from the police service in 2013, the former detective sergeant battled PTSD and major depression, seeking treatment at the Westmead Trauma Clinic as his marriage disintegrated.

“I had been plagued with suicidal thoughts and eventually I acted on them,” he says of that bleakest of moments in his Coffs Harbour home.

And then, the turning point. 

“I thought ‘this is never happening again’. I made that commitment to my eldest son, who drove me to hospital. When I got home, I sat there for a whole week and worked through everything that led me to where I was, and I made a game plan.”

Semple, who attended St Francis Xavier then got a labouring job at BHP thanks to his grandfather Hugh McCarthy, who led the Federated Ironworkers Association in the 70s and 80s, has now come full circle. 

“Moving back to Newcastle after 30 years away, I truly feel like I’m home again,” he says.

In 2017 he founded his training and development business Mentality Plus after gaining accreditation as a mental health first aid instructor.

The move came after a lot of self-care and soul-searching during his recovery.

“When I gave up [on life] I thought I had nothing left but there was still something there,” he says.

“I’ve got a lot of drive, and I’m really self aware, and I knew what I needed to do.”

Drawing on strategies he’d learnt in 250 hours of one-on-one sessions with clinicians during his recovery and making lifestyle improvements including daily exercise and quitting alcohol, Semple took stock and challenged his negative thinking.

“I look back at when I was sitting there doing my game plan and I had looked at my situation with a sense of loss – I had lost my 25-year career, identity and my health and I was losing my marriage, and I just thought I have to turn it all into a gain,” he says.

He contacted the Black Dog Institute to volunteer for fund-raising, but when they heard his story they asked him to be an educational presenter on mental health issues.

“I did my first talk before 170 high school kids and I was petrified, I nearly pulled out, I was opening up about my private life and I was only three months out of hospital,” he admits.

Afterwards, students lined up to share their own stories, including personal mental health issues and suicide affecting their families. 

That initial feeling of connection and positivity has led Semple to since deliver about 10,000 talks all over Australia.

“One year into the process I realised I had reached a turning point. It wasn’t a lightbulb moment, it was just realising that I was having more good days than bad...I was committed to my well-being strategies, I was challenging myself, I was socially reconnecting after being a recluse for three years, I was learning new skills,” he says. 

Semple’s volunteer work has had an enormous impact. It’s given him a sense of purpose that he once got in the “family” of the force, where danger, adversity and ultimately the spilling of blood bonded him to his colleagues. 

In 2016, he was selected as an inaugural mentor for the NSW Police Legacy program Backup For Life, providing support to injured police officers and their families.

Semple’s “lived experience” is at the forefront of both the mental health training presentations he does as a trainer contracted to Forsythes Training and corporate speaking engagements. 

“When people hear my background, they think if this can happen to this big bullet-proof former cop, it can happen to me...the resilience stuff gives them hope that recovery is possible,” he explains. “People come up to me after and say ‘I’ve been battling for eight years and you’ve convinced me to go to the doctor’, or ‘My daughter is going through this’. That’s where the power is, it’s pretty special.”

His mental health first aid course helps employees better identify if someone has a mental health issue or is developing one and learn how to approach it and get them professional help.

Warning signals for depression, he says, include if a person has a sustained low mood or starts to lose interest in all the things they enjoy. 

“Education gets rid of ignorance and creates empathy,” he says simply.

Semple resolutely practices what he preaches. 

He exercises daily, challenges negative thoughts, practices mindfulness and gratitude and volunteers. 

Not only has he rebuilt himself and his relationship with his three sons, he has a new career.

He’s also a better bloke.

“In the cops, I had a big ego and a chip on my shoulder. Depression strips you to nothing. I am so much more compassionate and empathetic than I was,” he says.

“Some things are so tragic in life and it’s hard to find gratefulness, but ... there is always something you can find to be grateful for. I went through all of that for a reason...There’s nothing that life can throw at me that I can’t handle. ”

Semple is quick to underline he is not cured – he still has lingering symptoms of PTSD.

“For a long time I was setting myself up to try and achieve that – I am in a point of recovery,” he clarifies. 

For him, recovery means returning to a point where he can work, contribute to his community and restore quality of life.

“Striving for recovery is so much more achievable – I mean, who is running around out there over the age of 35 who is symptom free of mental illness?” the 49-year-old says wryly.

“I’m more realistic about my expectations. People get carried away in seeking happiness. I just like to be content. That’s more achievable.”