Scream: A DCI Mark Lapslie Investigation by Nigel McCrery Read Free Book Online Page B

That means—’
    Lapslie finished the thought for her. ‘That means whoever recorded this sound file probably has so many files that theyhave problems with the storage, so they have to compromise the sound quality.’
    ‘So whoever is doing the screaming—?’
    ‘—is either not the only screamer—’
    ‘—or they’ve done a lot more screaming than just this.’
    The lab was silent for a while as the three of them absorbed the implications of what they had just worked out.
    ‘What else can you tell me?’ Lapslie asked quietly.
    Sara was considerably less bubbly now than when Lapslie and Burrows had come in. ‘I ran the file through a series of filters to reduce hum and static and to enhance the audio frequencies. First, judging by the slight echo on the screams, she’s in a large and relatively open space.’
    ‘She?’ Lapslie asked.
    ‘It’s definitely a woman’s voice. Analysis of timbre confirms that. Whatever it is that’s happening to her to cause her pain happens twenty-seven times. That’s the number of cries there are. And thanks to the fact that it’s a stereo recording we know that either she was moving around while the recording was being made or the person that made the recording was moving around.’
    ‘Either way,’ Burrows interjected, ‘it suggests that whatever is going on is not straight torture, with the victim restrained and the torturer standing over them. This was mobile.’
    ‘The recording is original and unedited,’ Sara added. ‘What’s there is what actually happened, from the moment the “Record” button was pressed to the moment the “Stop” button was pressed.’
    ‘How do you know?’ Lapslie asked.
    ‘We use a specialised piece of software to detect signs that a file has been edited. It was originally developed for use by the KGB, but it’s available on the open market now. It analyses anyrecording for signs of tampering, like changes in background noise, artefacts left by stopping and starting recording, and a whole load of other signatures that can be electronically detected.’ Her face darkened. ‘And I’m pretty sure that she dies at the end.’
    ‘Because …?’
    ‘Because of the very last sound.’ She turned to the computer and, using the mouse, highlighted a particular mountain peak at the end of the graphical representation. She pressed the ‘Play’ button on the screen.
    Lapslie drew his breath in sharply as the final moments of the sound file played: a low, indeterminate noise that still managed to chill the spine, despite its ambiguity.
    ‘That could be anything,’ he said.
    ‘It’s a death rattle,’ she replied. ‘The last breath catching on mucal secretions in the back of the throat. I’ve—’ She stopped, swallowed – ‘I’ve heard it on recordings before.
    He raised an eyebrow questioningly.
    ‘Usually last confessions from someone in hospital, recorded by a police witness,’ she added. ‘Not one of the more pleasant aspects of the job, but we have to be able to prove that they are genuine for the courts.’
    ‘“Life, like a child, laughs, shaking its rattle of death as it runs,”’ Lapslie murmured softly.
    Burrows frowned. ‘What?’
    ‘Nothing. Just a phrase.’
    ‘Oh,’ Sara said after a few moments, ‘I almost forgot. The file was recorded in the UK, probably in Essex.’
    ‘How do you know?’
    ‘Electrical Network Analysis. ENA.’
    Lapslie looked at her blankly.
    ‘If the recording device was connected to a mains supply thenthere’s going to be a modulation of the audio signal due to electrical network frequency fundamentals, their harmonics and sub-harmonics. We use specialist forensic software to detect the number and relative amplitudes of electrical network frequency components, detect what type they are – mains, uninterruptible power supplies, etcetera – and compare them to a database of various national mains supplies that’s been compiled by acoustic forensic experts across the world.