'Good thinking. Normaly the corpse acts as a shield for the soil, but stones would have had the same effect.'

'Does rain create problems?'

'In a protected environment the heavy, mucoidlike secretions produced from anaerobic fermentation bind the soil together, making dilutional factors from rainfal insignificant.'

He sounded like he was reading from one of his articles in the Journal of Forensic Sciences.

'Keep it simple, please. This is way off my field.'

'You spotted the decomp stain.'

'Actualy, my dog did.' I indicated a plastic vial. 'The pupae are what tipped me.'

Laslo withdrew the jar, twisted off the lid, and shook a number of casings into the palm of his hand. Each looked like a miniature footbal.

'So maggot migration had taken place.'

'If the stain is from a decomp espisode.' I'd had al night to worry over Boyd's discovery. Though I was sure his nose and my instincts were correct, I wanted proof.

'Maggot pupae definitely suggest the presence of a corpse.' He replaced the casings. 'I think your dog was right on.'

'Can you determine if it was an animal?'

'The amount of volatile fatty acids wil tel us if the body was over one hundred pounds. Very few mammals get that big.'

'What about hunting? A deer or bear could get that big.'

'Did you find any hairs?'

I shook my head.

'Decaying animals leave behind tons of hair. And bones, of course.

When an organism dies, scavengers, insects, and microbes take an immediate interest, some munching from the outside, others from within, until the body is reduced to bone. This is known as decomposition.

Ruby would talk in terms of dust to dust, but the process is much more complicated than that.

Muscle, comprising 40 to 50 percent of the weight of a human body, is composed of protein, which is composed of amino acids. At death, the fermentation of fat and protein yields volatile fatty acids, or VFAs, through bacterial action. Inside the gut, other microbes do their part. As putrefaction advances, liquids ooze from the body, carrying with them the VFAs. Death investigators cal the mixture soup.

Laslo's research focused at the microbial level, analyzing organic components contained in the dirt under and around a body. Years of work had demonstrated a correlation between the decay process and VFA production.

I watched him filter soil through a stainless-steel sieve.

'Exactly what do you look for in the dirt?'

'I don't use soil, I use soil solution.'

I must have looked blank.

'The liquid component between soil particles. But first I have to clean it.'

He weighed the sample.

'As body fluids flow through, the organic matter becomes bound to the soil. I can't use chemical extractants for separation, because that would partialy dissolve the volatile fatty acids from the decomposing body.'

'And alter their measurements.'

'Exactly.'