McKinsey advised drug companies on how to 'turbocharge' opioid sales. Now it's under criminal investigation.

• The Department of Justice is investigating McKinsey for advising opioid producers on boosting sales.
• The firm previously paid nearly $1 billion to resolve lawsuits related to its opioid work.
• The investigation is also looking at potential obstruction of justice by McKinsey and its employees.

Premier consultancy McKinsey & Company is under investigation by the US Department of Justice for its past work advising opioid manufacturers on how to juice sales, The Wall Street Journal reported on Wednesday.