Can't Let Go Threshold
Definition
Current level (10-20 mA for AC) at which sustained tetanic muscle contraction prevents voluntary release of a gripped conductor. Critical in domestic-appliance electrocution deaths.
- Current range
- 10 to 20 mA (AC)
- Mechanism
- Sustained tetanic muscle contraction
- Effect
- Prevents voluntary release of a gripped conductor
- Relevant context
- Domestic-appliance electrocution deaths
Common questions
Why is the let-go threshold forensically significant in electrocution deaths?+
Once grip current exceeds this threshold, the victim cannot voluntarily release the conductor, prolonging contact time and current exposure. This helps explain why some low-voltage domestic incidents prove fatal despite currents well below thresholds normally associated with severe injury.
How does the let-go threshold differ from the current that stops the heart?+
The let-go threshold, around 10 to 20 mA, is far lower than the current typically needed to induce ventricular fibrillation. Its forensic relevance is prolonged contact and exposure duration, not direct cardiac disruption, which occurs at substantially higher currents.
Does the let-go threshold differ between AC and DC current?+
Yes, the value is specific to AC because tetanic muscle contraction is driven by the repeated depolarization cycles of alternating current; DC produces a single sustained contraction on contact and release rather than the same inability to let go.
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