She strained her eyes, trying to draw out individual leaves and their skeletal branches.

No, there couldn’t be anyone there, don’t be stupid. It was just another of those things that lived in her head now. Scared of everything. Angry at everything. It wasn’t real and she needed to learn the difference again. Sweat on her hands, not blood. She walked up to her house, glancing back only once. The pill will take it away soon, she told herself. Along with everything else.

How do pathologists determine time of death in a homicide case?

The most important thing to note is that time of death can only ever be an estimated range; a pathologist cannot give a specific time of death, as we sometimes see in movies and TV shows. There are three main mortis factors used to determine the estimated time of death, and some of these tests are performed at the crime scene itself, as soon as possible after the victim is found. As a general rule, the sooner a victim is found post-mortem, the more accurate the time of death estimate.[1]

1. Rigor Mortis

Immediately after death, all the muscles in the body relax. Then, typically around 2 hours post-mortem, the body starts to stiffen due to a build-up of acid in the muscle tissues.[2] This is rigor mortis. It begins in the muscles in the jaw and neck, proceeding downwards through the body to the extremities. Rigor mortis is normally complete within 6-12 hours, and then starts to disappear approximately 15-36 hours after death.[3] As this stiffening process has a roughly known time of occurrence, it can be very useful in estimating time of death. However, there are a few factors that can impact the onset and timeline of rigor, such as temperature. Warm temperatures will increase the rate of rigor, whereas cold temperatures will slow it down.[4]

2. Livor Mortis

Also known as lividity, livor mortis is the settling of the blood inside the body due to gravity and the loss of blood pressure. [5] The skin will become discoloured with a red/purple tinge where the blood has pooled internally.[6] Livor mortis starts to develop 2-4 hours after death, becomes non-fixed up to 8-12 hours after death, and fixed after 8-12 hours from the time of death.[7] Non-fixed refers to whether the skin is blanchable: this means that – when lividity is present – if the skin is pressed, the colour will disappear, a bit like when you press your own skin now. [8] But this process can be affected by factors such as temperature and changing body position.

3. Algor Mortis

Algor mortis refers to the temperature of a body. After death, the body starts to cool until it reaches equilibrium with the ambient temperature (wherever the body is discovered).[9] Typically, the body will lose about 0.8 degrees per hour, until it reaches the environmental temperature.[10] At the crime scene – in addition to making observations about the rate of rigor and lividity – a medical examiner will also likely take the body’s internal temperature and that of the environment, in order to calculate approximately when the victim was killed.[11]

Although these processes cannot tell us the exact minute a person died, they are the main factors a pathologist uses when estimating a range for the time of death.

Death stared back at her. Real death, not the clean idealized version of it; the purpling pockmarked skin of a corpse, and the eerie forever-whitened imprint of a too-tight belt they must have worn as they died. It was almost funny, in a way, Pip thought as she scrolled down the page on her laptop. Funny in the way that if you thought about it too long, you’d go mad. We all end up like this eventually, like these postmortem images on a badly formatted web page about body decomposition and time of death.

Her arm was resting on her notebook, steadily filling up with her scribbles. Underlines here and highlighted parts there. And now she added another sentence below, glancing up at the screen as she wrote: If the body feels warm and stiff, death occurred three to eight hours prior.

‘Are those dead bodies?!’

The voice pierced through the cushion of her noisecancelling headphones; she hadn’t heard anyone come in. Pip flinched, her heart jumping to her throat. She dropped her headphones to her neck and sound came rushing back in, a familiar sigh behind her. These headphones blocked almost everything out, that’s why Josh kept stealing them to play FIFA, so he could ‘noise-cancel Mum’. Pip lurched forward to switch to another tab. But, actually, none of them were any better.

‘Pip?’ Her mum’s voice hardened.

Pip spun her desk chair, over-stretching her eyes to cover their guilt. Her mum was standing right behind her, one wrist cocked against her hip. Her blonde hair was manic, sections folded up into foil like a metal Medusa. It was highlighting day. They happened more frequently now that her roots were starting to show grey. She still had on her clear latex gloves, smudges of hair dye on the fingers.

‘Well?’ she prompted.

‘Yes, these are dead bodies,’ Pip said.

‘And why, darling daughter, are you looking at dead bodies at 8 a.m. on a Friday morning?’

Was it really only eight o’clock? Pip had been up since five.

‘You told me to get a hobby,’ she shrugged.

‘Pip,’ she said sternly, although the turn of her mouth had a hint of amusement in it.

‘It’s for my new case,’ Pip conceded, turning back to the screen. ‘You know that Jane Doe case I told you about. The one who was found just outside of Cambridge nine years ago. I’m going to investigate it for the podcast while I’m at uni. Try to find out who she was, and who killed her. I’ve already been lining up interviews over the next few months. This is relevant research, I swear,’ she said, hands up in surrender.

‘Another season of the podcast?’ Pip’s mum raised a concerned eyebrow. How could one eyebrow communicate so much? She’d somehow managed to fit around four months’ worth of worry and unease into that one small line of hair.

‘Well, I’ve somehow got to fund the lifestyle to which I have grown accustomed. You know, expensive future libel trials, lawyer fees...’ Pip said. And illegal, unprescribed benzodiazepines, she thought secretly. But those weren’t the real reasons; not even close.

‘Very funny.’ Her mum’s eyebrow relaxed. ‘Just... be careful with yourself. Take a break if you need it, and I’m always here to talk if...’ She reached out for Pip’s shoulder, forgetting about the hair-dye covered gloves until the very last second. She stalled, lingering an inch above, and maybe Pip imagined it but she could somehow feel the warmth from her mum’s hovering hand. It felt nice, like a small shield against her skin.

‘Yeah,’ was all Pip could think of to say.

‘And let’s keep the graphic dead bodies to a minimum, yes?’ She nodded at the screen. ‘We have a ten-year-old in the house.’

‘Oh, I’m sorry,’ Pip said, ‘I forgot about Josh’s new ability to see through walls, my bad.’

‘Honestly, he’s everywhere at the moment,’ her mum said, lowering her voice to a whisper, checking behind her. ‘Don’t know how he does it. He overheard me saying fuck yesterday, but I could’ve sworn he was on the other side of the house. Why is it purple?’

‘Huh?’ Pip said, taken aback, until she followed her mum’s eyes to the laptop screen. ‘Oh, it’s called lividity. It’s what happens to the blood when you die. It pools on the... Do you really want to know?’