The X26C marks a move into the US consumer market

Taser shares fell 17.74% to $22.72 on the news but the firm said it was confident studies backed up its claims.

Last year, an Amnesty International report said Taser's high-voltage weapons have been linked to more than 70 deaths in the US and Canada.

The SEC will also look at the timing of an announcement on a distribution deal.

Taser's products are used by American law enforcement agencies and have also been tested by police forces in the UK.

Consumer market

In December the company said it had signed a $1.5m (£800,000) deal with firearms dealer Davidson's to distribute its X26C device.

The X26C marks Arizona-based Taser's first move into the US consumer market.

The timing of the news, however, was questioned by some stock watchers, with Gradient Analytics saying had Taser not made the announcement about the deal it would have been forced to report its first quarterly sales fall in nearly two years.

Taser, however, pointed out that the order from Davidson's - a customer since 1999 - came during the "normal course of business" in the final three months of the year.