All four police forces in Wales look set to deploy 50,000-volt stun guns to tackle violent suspects.
The Gwent force is introducing Taser guns from Monday while it has already been used by North Wales Police.
On Sunday, it emerged the Dyfed-Powys force was training officers to use the weapon, while South Wales Police says it will probably introduce it shortly.
Amnesty International claims the guns have been linked to more than 70 deaths in America and Canada.
The Taser guns work by firing two darts up to 21 feet at a target, each trailing a wire which delivers a high-voltage shock that can disable suspects in order for them to be arrested. The electrical current can penetrate clothing up to two inches thick.
The guns have been welcomed by some senior police officers as an effective but non-lethal method of halting a violent offender.
The US-based manufacturers of the device insist that it causes no long-term injuries and only short-term skin irritation.
Dyfed-Powys Police has started training officers to use Taser guns
But critics argue Taser shocks can induce a fatal reaction in people with underlying heart problems or with large quantities of drink or drugs in their blood.
North Wales Police was one of the first UK forces to use the weapons on the streets when a man in Rhyl was fired at three times in August 2003.
The man was examined later by a police surgeon for minor injuries but was found to be otherwise fit and well.
Gwent Police Chief Superindendant Alun Thomas said the Tasers used by his force have a micro-computer to record exactly how they are used.
He said: "The Tasar along with baton guns have never been deemed as "non lethal", we recognise there's always going to be a risk.
"There have been trials in the UK and they have been shown to be very effective.
"They do provide us with yet another option in our armoury... without recourse to live weapons."
He added that a high-ranking officer would need to give permission before the weapon could be deployed.
On Sunday, Dyfed-Powys Police confirmed it has been training officers in how to use the weapons.
A spokesman for South Wales Police said it had no firm plans to introduce the weapon but said it probably would follow the trend to bring them in.
Amnesty International claims more than 70 people have died in the USA and Canada after being struck Tasers.
Spokesman Huw Thomas said: "We certainly don't think it's appropriate for Gwent police to introduce them, nor any other force.
"We're not asking for a total ban on Tasers, but the point is that the long-term effects havn't been tested enough.
"People have been known to die when they're under the influence of alcohol or drugs having been shot by one of these things."