Putting someone in prison for 5 years in error is also highly problematic, yes. The argument the parent is making applies to incarceration, but it applies more

Putting someone in prison for 5 years in error is also highly problematic, yes. The argument the parent is making applies to incarceration, but it applies more urgently to the death penalty. The parent already makes your point by (hypothetically) applying an percentage error rate that would be acceptable.