New book details how Australians can help solve three unexplained killings in NSW

Three families are clinging to hope the mystery of their loved ones deaths will finally be solved. The forensic expert who worked on their cases reveals why he thinks it’s possible.

Exclusive: A slain woman’s arm protruding from a shallow grave, a businessman found dead in a luxury apartment, and a body found mysteriously floating in Sydney Harbour.

These are three grisly crimes forensic toxicologist Dr William Allender is hoping ordinary Australians can help solve.

Dr Allender helped police bring killers to justice for decades – including his sensational discovery a sex drug may have killed Dr Gilbert Bogle and Margaret Chandler in 1963.

Dr Bogle, 38 and his lover Margaret Chandler, 28, were found dead on the banks of Lane Cove River in Sydney on New Year’s Day 1963.

Several investigations and coronial inquiries couldn’t determine how they died, until Dr Allender found traces of Yohimbine, a drug widely to treat erectile dysfunction.

Now retired, he is hoping his new book The Expert Witness: A Second Dose will help give the families of three victims closure.

Toxicologist Dr William Allender has written a book about some of the most fascinating cases he has worked on, including cases that remain unsolved. Picture: Sue Graham

“That would be a wonderful outcome,” Dr Allender said of the cases he thought would “tantalise” readers.

Katrina Ploy was found floating in Sydney Harbour on Christmas Day 2006 – her clothes were found at the top of a cliff, but a post mortem revealed a non-lethal level of MDMA and no injuries consistent with a fall.

“She hadn’t overdosed and she didn’t have any damage to her body at all, which one would expect from jumping off a cliff. So it’s a mystery that hasn’t been solved today. Hopefully, someone who reads this will be able to,” he said.

Maureen McLaughlin was 23 when she was murdered in 1992 – her body was discovered by a woman collecting flowers who saw an arm sticking out of a mound of dirt in Lithgow.

Katrina Ploy’s body was found din Sydney Harbour but her death remains unexplained.

Ms Ploy’s car was found a week before her body was discovered in Watsons Bay, Sydney.

Dr Allender's new book, The Expert Witness: A Second Dose

“It must have been a shocking sight for the bushwalker to find. She’d been buried in shallow grave where a dog had been previously been buried. And initially when it was excavated, we thought it was actually a carpet [but] she’d been buried on top of the dog,” he said.

“It was possibly strangulation, but there was nothing we could prove. So I’m counting on people out there that knew that situation and were willing to come forward and provide the final piece in the jigsaw puzzle,” Dr Allender said.

One chapter of the book is titled ‘Sex, drugs and the death of a businessman’ and details the death of French businessman David Monlun.

Maureen McLaughlin’s body was found in a shallow grave.

David Monlun died from a drug overdose, but the circumstances remain unclear. Picture: Supplied

Mr Monlun, 40, either overdosed or was deliberately given GHB at his Darling Harbour apartment in what a NSW Coroner referred to as a “salacious” case.

“He was quite a wealthy businessman and unfortunately he passed away in rather suspicious circumstances. Hopefully someone will have further evidence that will solve this particular matter,” Dr Allender said.

He admits his line of work could be gruesome “but someone has to do it”.

“There’s folk like myself out there that set out to solve these matters, and hopefully bring closure for the family. So they know what actually happened and why it happened,” he said.

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Originally published as New book details how Australians can help solve three unexplained killings in NSW