Patricia Cornwell is no stranger to guns. She's big on personal security and never wants to leave herself vulnerable.

"I wouldn't call myself a gun expert but I am very familiar with firearms," the bestselling forensic thriller writer explains.

"I've owned a number of them throughout my life, particularly when I lived in places where I needed that form of protection, but more importantly, it's part of my research."

The author, who began her career as a reporter and then worked at the office of the Chief Medical Examiner in Richmond, Virginia, still subscribes to a lot of different services to keep up with what's going on in the field, and has many professional contacts who will fill her in on the latest technologies, she explains.

The last time we met, three years ago, a bodyguard stood outside her London hotel suite throughout our interview and the security-conscious author - whose forensic mysteries, including Postmortem and The Body Farm, have sold more than 100 million copies and made her millions of dollars - admitted her fears are greater because she's seen so many crime scenes, and knows what one human being can do to another.

Today, she tells me about her visit to a firing range in Texas to try out some of the newest, most high-tech weaponry, so she could write accurately about the gun in her 22nd Scarpetta novel, Flesh And Blood, which sees her heroine, forensic sleuth Dr Kay Scarpetta, on the hunt for a serial sniper who leaves no evidence except fragments of copper.

"You need to worry about firearms which have tremendous range and accuracy potential, even in the hands of someone who's not a trained sniper, and about the protection of those who could be at risk, that maybe the perimeter of what used to be a safe distance away now has to be twice as long."

Her novels could give us a lot to worry about, yet Cornwell doesn't believe that the criminal possibilities that are explored in her books will give ideas to real criminals in the real world.

"I don't think potential criminals, who are driven by their own intense motivations, whether they are psychopathic or power-hungry, need me to give them ideas. They are going to come up with what works for them."

Her own life has seen almost as much drama as her books, and accounts of her miserable childhood, struggles with anorexia and alcohol and her outing as a lesbian, as well as legal battles and public fights with ex-lovers, have been well documented.

Born in Miami, Cornwell's father, a lawyer, walked out on Christmas Day, ignoring his five-year-old daughter's attempts to cling to his leg. Her mother moved to an evangelical community in North Carolina, down the road from famous preacher Billy Graham and his wife.

For years, Cornwell had no idea that she could be gay. While studying English at college in North Carolina, she fell in love with her male professor, Charlie Cornwell. They married but ended up divorcing after 10 years.

She did have lesbian encounters subsequently, but kept her sexuality a secret - until she was outed by several so-called friends who informed the media.

"They were not happy about the huge success I was having and decided they wanted to be damaging," she has said. "Jealousy is a terrible thing. Then it became sensational and I wasn't ready for so much detail about my life to be disgorged in articles which were extremely nasty."

However, like her forensic sleuth Scarpetta, Cornwell, 58, has mellowed, she reflects. It's almost 25 years since the character first appeared in Postmortem, and they have matured together, it seems.

"She has changed a lot, as you would hope any human being would after so many experiences. She's become much more thoughtful and reflective. She doesn't just barge on through to try to solve something. She's much more philosophical and less judgmental. She was pretty hard-headed in the earlier books and she's mellowed."

Scarpetta is now happily married to FBI profiler Benton Wesley, and still playing guardian angel to her switched-on gay niece Lucy, while Cornwell has been happily married to Staci Gruber, a Harvard academic, for nearly 10 years. She dedicates the latest book to her.

"Scarpetta reflects my history a lot, which is inevitable when you spend so much time with a character. I think her point of view is the right one.

"I'm more mellow. You get some wisdom with time. Looking back to my 40s, when my career hit the high zone of success, I think I'm very different now to how I was then.

"You get a little less adamant. With time, you see different perspective, and see that there are not just two sides to a story. I don't rush to battle as much as I did."

Yet there have been recent battles. Last year, she reportedly won punitive damages worth 50million US dollars in a lawsuit against her former accountants.

"It's not over yet," she reveals. "Once you get to the post verdict stage, you can be into years of motions that are filed and possible appeals. We are still very much involved in this case. People think you walk out of the courtroom and get handed a cheque, but it doesn't work that way.

"But I'm not sorry we got into it. We tried to right an injustice that we couldn't live with. I don't regret doing it."

She'll never kill off Scarpetta - that would upset too many fans, she says - and still hopes that her forensic sleuth will one day appear on screen.

"I do think it will happen, but the only way to go is to make it unusual, to make it something people aren't expecting. When I first started out, everybody wanted to do a movie about Scarpetta, because there was nothing out there like that. Now, there's nothing different.

"You'd have to introduce her to the public in a way that doesn't come across as a crime procedural or a CSI-type show. It needs to be something that explores the many layers of her character."

Her books have also had to change with the times.

"I don't need to spend 20 pages showing you an autopsy any more, because you can watch one on television. I don't need to explain what an FBI profiler is any more."

She has just signed a deal with CBS for an original television drama she's created, featuring a character called Angie Steele, an unorthodox detective who works for San Diego's major crimes unit. She's also started the next Scarpetta, although distractions are ever present.

She and Gruber live in a condominium in Boston and Cornwell's office is nearby. But there are periods when she escapes to Florida or California on her own to write.

"I'd much rather tweet, Facebook, email, get on the phone or go for a walk with Staci. I can tell you a million things I'd rather do than write. It's the best thing I ever do, but it's also the hardest."

:: Flesh And Blood by Patricia Cornwell is published by HarperCollins, priced £20. Available now