HE is Scotland's leading criminal defence lawyer who has devoted his life to his job.

But Donald Findlay QC has, for the first time, told of the toll his work has taken, describing it as at times "distressing".

The flamboyant advocate - known for puffing on his pipe and for his mutton-chop sideburns - has lead the defence in some of Scotland's most infamous murder cases, including Peter Tobin and Luke Mitchell.

Now 68, he has also offered insight into the inspiration for his decision to pursue such a career, going back to his childhood in the 1950s when he first read about the Scottish serial killer, Peter Manuel.

Findlay, who hails from Cowdenbeath, Fife, opens up in a new BBC Scotland series, Crime Files, which begins on Sunday.

Interviewed by renowned Scots criminologist, Professor David Wilson, he hints at harbouring regret over allowing his job to become his life - but suggests that it is now too late to change his ways.

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“I’ve never really acquired any hobbies or interests or anything outwith the job," he says.

"It’s constantly just a part of my life and has now been so for well over 40 years.

“I tell young lawyers who want to become involved in crime, it is a vocation because it’s not easy to defend some of the things we have to defend and you’ve got to do it with a passion and you’ve got to do it with a vigour.

“But at the same time, you shouldn’t do what I’ve done and let it become the be-all and end-all. It’s too much. I know that now but it’s a bit late.”

He is, though, chairman of his hometown football club, Cowdenbeath FC, but admits there is “no pleasure” in the role, adding: “If you look to see the record of Cowdenbeath... you will see that this is another burden I have to carry around with me.”

He also says that everyone is entitled to a defence, but admits there is a downside to his position: “If you believe in the legal system, you believe that everyone is entitled to a defence. Then you can’t pick and choose.

“You can’t say, ‘Well, I’ll defend somebody who does this, but I’m not going to defend somebody who commits a sexual offence or a mass murder, or whatever', because that’s just not right.

"You take on somebody who’s accused of crime and you defend them in respect of that crime.”

But he admits to finding it “difficult sometimes” due to how up-close-and-personal his position takes him to man's inhumanity to man.

One of his most successful defences was that of former gangster Paul Ferris, who in 1992 was found not guilty of all seven charges against him, including that of murdering Arthur Thompson Jr.

He also defended Mitchell, who in 2005 was sentenced to life imprisonment for murdering his 14-year-old girlfriend, Jodi Jones, and Tobin. Now 72, he will die in jail, having been convicted of the murders of Angelika Kluk in Glasgow in 2006, Vicky Hamilton in 2008 and Dina McNicol in 2009.

Tobin also features in the Crime Files series, in which Professor Wilson, who grew up in Carluke, maintains the killer is also infamous Barras dance hall murderer Bible John.

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Findlay says: “I do worry. I worry about what is happening during a trial. I tend to take work home with me, and after a trial if the client has been convicted then I worry that perhaps I could or should have done better.

"But during a trial you do see some pretty horrendous things. Man’s inhumanity to man is pretty endless and you just have to harden yourself and look as it as best as you can as a piece of evidence.

“But some things I have looked at can be quite distressing, involving dead children and so on.”

As a seven-year-old in the 1950s, it was reading about Manuel that lead him toward his career. The US-born serial killer, who moved to Uddingston, Lanarkshire, was convicted of murdering  seven people across Lanarkshire and southern Scotland between 1956 and his arrest in January 1958, but is thought to have murdered two more.

Earlier this year, Findlay narrated an audiobook detailing the life of Manuel, who was taken to the gallows at Barlinnie in 1958 after one of the most sensationalist trials in legal history that saw him sack his lawyers and conduct his own defence.

When the 14-hour audiobook, Manuel: Portrait of a Serial Killer, was released, Findlay said: "The Manuel case fascinated me since I was a child. As a seven-year-old, I read every word that was reported.

"The challenge of representing someone faced with so many serious charges is one of the reasons I became a defence lawyer."

Findlay also says during the programme that the increasing use of science by prosecutors in court cases is a "very real concern", in part because some can form views by watching TV.

He says: “One problem is, members of the public get a lot of their science from CSI: Miami and New York and all these kind of things. And that’s not real. But that’s the impression you get.

“People think it’s as simple as that but, of course, it’s not. So you really have to understand science, you have to be wary of science because there’s a lot of junk science out there."

Crime Files begins on Sunday on BBC Scotland at 9pm.