In 1985 British DNA scientist Helena Greenwood was brutally murdered in San Francisco.

The only suspect, Paul Frediani, could not be linked to the crime.

In 1999, a San Diego detective reopened the case – armed with a vital clue and a new forensic weapon that Greenwood helped pioneer …

Sydney Greenwood raises himself from his armchair, in his boxy brick house down a quiet street in Lymington, a pretty town on the south coast of England, and fetches a pile of photographs of his daughter Helena from a walnut box. They slither through his dry hands and on to a rickety side table. They are mainly black and white, taken by a professional photographer when Helena was in her mid-teens. She is in a slightly different position in each picture, and looking at them together, they appear like an animated film, or one of those childhood flick-books, which come alive when you ruffle through them. The overwhelming impression given by these photographs is of serenity - she is looking away from the camera with large, steady eyes, her lips are parted slightly and there is a gap between her front teeth wide enough for an old shilling coin; her hair is long, worn parted on the right, with wisps straying across her forehead. 'She never told us about the sexual assault. She said she had been burgled, but nothing else. Her mother was ill and she didn't want to worry us, you know,' he explains.

Helena Greenwood was born in the summer of 1949, in a village not far from where her father lives now. She grew up under the pale English sun, with a bucket and spade and floppy hats, adored by her parents, two gentle academics. 'She was always a very happy young girl,' Sydney says. 'She was gregarious, full of the wonders of the world. We took her everywhere. We had this little cottage in Wales, very basic, no electricity, near a stream, where we would watch the kingfishers, and the sea trout come up in autumn. Helena would walk down to the stream to collect water and come back with two heavy buckets. She was only a mite then, but she was always very determined, oh yes.'

He sinks back into his chair, closes his eyes, as if replaying the scene on the blank space behind his lids. Sydney Greenwood is eighty-seven. The passing years and tragedies have etched their stories on his face, gaunt but still handsome. At certain angles and with certain expressions, he could be mistaken for Peter O'Toole. He is warm and welcoming, and when he smiles, a whiff of mischief passes over his features. But inside his body, cancer is nibbling away at his organs; he knows his time is near.

'We doted on her, Marjorie and I. Marjorie was a geologist, y'know, a very clever woman.' He points to a silver-framed photograph across the room, of a scruffy-haired woman, standing on a moor in winter, looking at the camera with dark-eyed intensity. 'That is where Helena got her brains from. We were very concerned that she would miss out on a lot, as an only child, so we tried to get her to meet other young children. She was a bit of a ruffian, really, she was quite one of the bosses of the gang. But she was a very good girl.’

'She wasn't outstanding at school, mind. Not at first. She was just a typical girl of her age. She loved going to parties, shopping for clothes with her friends, oh, she was probably the best-dressed girl in Europe in her teens. Then she moved to another school, which had the staff to cope with science. It really fired her interest. Suddenly, we couldn't stop her doing her homework.' He laughs, a genuine ho-ho chuckle. 'I think she was always interested in science - she loved playing with bits of dirt and pebbles and things like that, a puddle in the wild west of Ireland, or a stream in Iceland. And she could read a map and take us through the city when she was six.'

Over several days, between cups of tea and impromptu snoozes, Sydney Greenwood paints a verbal picture of his daughter, every bit as vivid and vibrant as his oils and watercolours of sea- and landscapes that hang around the house, and rest stacked against the wall in his lean-to studio. Helena was determined, strong-willed, kind and loyal. She loved to cook, to make jewellery. She was scared of water: on a sailing trip with her parents when she was four, she had dropped her doll, hand-knitted by Marjorie, over the edge of the boat. The doll was rescued, but it shrank when it dried, and its eyes fell off. For many years after that, she would only walk above the high-water mark.

She met Roger Franklin when she was fourteen, a gangly grammar-school girl in a blue pleated skirt. He was two years older, at the boys' school along the road, soft-spoken, gentle, with a shy, gummy smile that made him look younger than his age. Perhaps not Helena's equal academically, he was rugged and courageous, a first-team sportsman. He adored her from the moment they met, and once their romance had been kindled three years later, there was no way he was going to let her go. On weekends, they would go for walks in the New Forest, and after a while, Roger persuaded her out of her fear of water and into a sailing boat with him. Sydney and Marjorie liked him, but 'Well, who is ever good enough for your only daughter?' they would say.

When she went up to Sheffield University, Roger studied landscape design, but their relationship survived the geographical separation. Helena buried herself in her studies. She was a hard worker, ambitious, sure of herself and of her vision of the world. As she progressed up the educational ladder, her talent for science became increasingly obvious; by the time she was twenty-four, she was working on a Ph.D. in chemical pathology at St Bartholomew's Hospital in London and had sent articles to several prestigious academic journals. She knew her future lay in science, and already she was turning her attention to DNA, the molecule that was reorienting the worlds of biology and chemistry, smashing pre-conceptions and opening vistas that spread from pre-birth to eternal life.

Roger was also part of her future. When she moved to London, he came with her. But it was their landlady who persuaded them to get married; she refused to let them a flat unless they were wearing rings on the appropriate fingers.

Silver invitations were sent out. Inside, Sydney had drawn a map of the route from the village church in Boldre to the Greenwoods' house, illustrated with ponies and cows and fish by the stream. On 20 September 1975 at noon, the same year as Helena became Dr Greenwood, they were married. It was a wonderful ceremony, and afterwards they celebrated in a large marquee on the lawn. Helena wore flowers in her hair and laughed when they cut the cake.

It was soon afterwards that they emigrated. Five years earlier, before Helena had started her Ph.D., they had worked their way across the United States with three friends, and from that moment, they had started talking about moving across the Atlantic. It was Helena's enthusiasm and fervour for her work that finally persuaded them; on that first trip she had seen that in America it was possible for a woman to make a career out of science. So a year after she had collected her doctorate, they packed everything they owned and flew west. The Bay area of San Francisco was a natural choice. It was the seed bed of the budding biotechnology industry, and Helena quickly found a job in Palo Alto, in the research laboratories of Syva, one of the leading firms in the field of medical diagnostics. The salary was many times what she could have hoped for in England - so she paid the bills while Roger completed his master's degree in Landscape Architecture at the University of California in Berkeley.

As a couple, they complemented each other, and had little need for friends. Many people who met them thought they were reserved, even stand-offish, by affable American standards. But a few managed to break through and saw a different side. Thomas and Patricia Christopher met Roger and Helena soon after they arrived, and the four of them struck up a close friendship. When Helena's and Roger's lease expired on their first house in Berkeley, they moved to an apartment near the Christophers' in Oakland, and when they eventually bought 90 Walnut Avenue, their first house, across the bay in Atherton, the Christophers helped them move. They went to jazz clubs, skiing and on camping holidays in the state parks of California and in Hawaii. The Christophers learned to laugh at Helena's organizational fetishes - she never travelled without a full library of guidebooks and would arrive at breakfast with a daily agenda.
 
Helena was doing well at Syva, working her way up towards the top bench. She soon realized, however, that she did not want to spend the rest of her career hunched over a microscope. There were scientific geniuses aplenty, constantly coming up with new and exciting ideas - but where the company fell down was in marketing and selling them. They were two different communities; the white coats and the suits. Helena believed she could be a bridge between the two.

She moved into product development, and from there to marketing. Denise Apcar, who joined the marketing department two weeks after Helena's appointment, thought highly of her. 'I was small fry then, but I watched Helena and I was very impressed by her professional demeanour. Yes, she was aloof, but I put that down to her British style.' It wasn't a very biotech style, though. This was an industry in its infancy, and most of the people employed in it had barely removed the braces from their teeth. They came to work in jeans, joshed each other and sprawled on sofas in their coffee break. Helena, with her nylon tights, bad haircuts and clipped vowels, was an outsider. And she made no effort to change that. When she felt that members of her team weren't pulling their weight, she was not shy to tell them, which rankles among some, to this day.

Sam Morishima, however, saw beneath the professional patina, and quickly became devoted to Helena. He had been raised in the strawberry fields of northern California by his Japanese immigrant parents, and was used to getting up with the sun for fifteen back-breaking hours filling plastic punnets. 'I always just felt lucky to be working in a temperature-controlled environment.' He first met her when he joined her international marketing team, and soon afterwards, she asked him out to lunch. 'I was so surprised. Helena was strictly business, and kind of separated from the group. I was in awe of her, but I didn't know her at all. Then she took me to this German restaurant, The Black Forest. I saw a completely different Helena. I had always thought she was really beautiful, but she had seemed so serious. That day I saw another side. When she smiled it was like you were playing in a playground with swings,' he says now, with a wide smile of his own. 'When she explained her philosophy it really made sense to me. She taught me that marketing was like shining a spotlight on your product, showing what it could do. For her it was not about deception, or making money, it was about helping millions of people. She believed that. It was her philosophy and she passed it on to me.'

Syva's main product was a system, known as Emit, used to detect the presence of drugs - both therapeutic and abused - in the blood chemistry. Its primary markets were hospitals and hospital labs, but Emit was increasingly being sought by forensic laboratories, to test for cocaine and barbiturates in urine. It  was a tense time. Syva had poured more money than it could afford into a new, automated drug-testing machine. If it worked, it would have dominated the field. But there were technical hitches and Abbott, Syva's main competitor, got their product out first. It was a disaster for Syva -they were forced to lay off hundreds of staff and cancel future projects. In a highly geared industry, one expensive mistake is enough to make you drown. But Helena was determined not to let that happen. With Sam Morishima, she worked through weeks of nights, reconfiguring the instrument until it passed international standards. 'We broke every rule,' Sam remembers, 'rewrote the software and got it into the international market. Helena loved that.' And the Syva board loved her: the strong international sales were a life raft for Syva, they saved the company. Helena was riding high. Her staff might not all like her, but they now knew they needed her.

Then there was the sexual assault. It was as if a curtain had been drawn across Helena's eight years at Syva. She told no one at her office - it wasn't her habit to chit-chat, and she would have hated the curiosity, the pity, the knowing looks. She was determined to act as if nothing had happened. So, on Monday 9 April, she went into work. She may have looked a little more tired, seemed withdrawn, but even if they had noticed, no one would have commented. She just swathed herself in an untouchable air and got down to work. Business as usual.

The Monday evening after the assault, Roger went with Helena to Atherton police station to meet Detective Stephen Chaput. Roger had jumped on the first plane back from Washington, and when Helena met him at the airport, the day after the assault, and Roger held out his arms, she had crumpled into them.

‘As fascinating a detective story as you could hope for’ 
Daily Telegraph

‘Compelling and disturbing’ 
Guardian

‘A wonderfully written, tightly paced thriller. One-part courtroom drama, one-part history lesson and two-parts detective story’ 
Sunday Tribune

‘Reads like a cross between Matt Ridley’s Genome and the latest courtroom thriller from Scott Turow. The best kind of non-fiction’ 
Mail on Sunday

‘An absorbing true-life murder story’ 
Observer

‘Deserves a permanent place on anyone’s true crime shelf’ 
Literary Review

* * * * * * Winner of the CWA Gold Dagger for non-fiction 2003 * * * * * * *

In 1985 British DNA scientist Helena Greenwood was brutally murdered in San Francisco. The only suspect, Paul Frediani, could not be linked to the crime.

In 1999, a San Diego detective reopened the case - armed with a vital clue and a new forensic weapon that Greenwood helped pioneer ...

The story of how a dead woman's groundbreaking work led to the solution of her own murder.

Samantha Weinberg has worked as a journalist in southern Africa, the United States and London. She is the author of Last of the Pirates and A Fish Caught in Time: The Search for the Coelacanth, which was a top 10 bestseller. She lives in Wiltshire.

Praise for Pointing from the Grave

?As fascinating a detective story as you could hope for, told by Weinberg with extraordinary clarity and simplicity? Daily Telegraph

?Compelling and disturbing weaving together the microscopic world of molecular biology with the drama of a murder investigation? Guardian

?A fascinating, wonderfully written, tightly paced thriller. One-part courtroom drama, one-part history lesson and two-parts detective story? Sunday Tribune

?A page-turning thriller the suspense is almost unbearable. Marvellous? Evening Standard

?Invaluable. Deserves a permanent place on anyone?s true crime shelf? Literary Review

?Reads like a cross between Matt Ridley?s Genome and the latest courtroom thriller from Scott Turow. Impeccably researched and fluently written, the best kind of non-fiction: straightforward enough for the layman, but with the intellectual rigour and balance of authentic scholarship? Mail on Sunday

For further information, please contact Anna Ridley on 020 7010 3251 / anna.ridley@penguin.co.uk