Yesterday, Twitter was issued a summons for a new lawsuit against the company, holding the service indirectly responsible for the ISIS-linked killing of an American contractor named Lloyd Fields in Jordan last year. The suit is a civil rather than criminal charge, but if found guilty, Twitter would be liable for triple the damages incurred by Fields' death.

Fields was killed on November 9th, 2015, when a Jordanian police captain named Anwar Abu Zaid opened fire in the cafeteria of the International Police Training Center in Amman, where Fields was teaching police and security skills. Zaid appears to have operated with relative independence, but ISIS outlets later claimed responsibility and there is evidence he had been inspired by earlier ISIS attacks on Western targets.

There's no evidence that Twitter software or networks were used in the planning of the attack, and Fields' lawsuit does not make that claim. Rather, the lawsuit alleges Twitter has fueled the growth of ISIS at large, which in turn gave rise to the attack that killed Lloyd Fields. "Without Twitter, the explosive growth of ISIS over the last few years into the most-feared terrorist group in the world would not have been possible," one passage reads. The complaint also alleges an estimated 70,000 ISIS accounts on Twitter and more than 30,000 foreign actors recruited through the platform in 2015. The suit also details widespread ISIS fundraising on Twitter, although it does not name a dollar amount.

Reached by The Verge, a Twitter spokesperson gave the following comment:

While we believe the lawsuit is without merit, we are deeply saddened to hear of this family's terrible loss. Like people around the world, we are horrified by the atrocities perpetrated by extremist groups and their ripple effects on the Internet. Violent threats and the promotion of terrorism deserve no place on Twitter and, like other social networks, our rules make that clear. We have teams around the world actively investigating reports of rule violations, identifying violating conduct, partnering with organizations countering extremist content online, and working with law enforcement entities when appropriate.Notably, the lawsuit includes recent statements about ISIS's Twitter presence from a number of US officials, offered as support for the idea that the service is responsible for Fields' death. FBI director James Comey is quoted as saying that ISIS uses Twitter "to crowdsource terrorism." Hillary Clinton is also quoted, saying Twitter is "going to have to help us take down these announcements and these appeals."

Twitter's legal defense is likely to center around the Communications Decency Act, which has traditionally exempted online services from liability for statements and activities that occur on their hosted network. However, Fields is putting the company on trial under a special terrorism statute, which may complicate that defense.

If successful, the suit is likely to have far-reaching implications, both for counterterrorism efforts and social media at large. ISIS is also very active on Instagram, and a number of US intelligence groups have used such networks as a means to gather intelligence. At the same time, Twitter's efforts to suspend ISIS accounts have often over-reached, as when the company mistakenly suspended an Arab Spring activist in December.