What you should know about ghost guns as Biden announces new regulation

A ghost gun used by a shooter in New York is seen on September 27, 2021.

(CNN)President Joe Biden on Monday announced new steps aimed at regulating so-called "ghost guns," as use of the untraceable, homemade weapons in violent crimes rises.

Ghost guns are one of many issues facing regulators and policymakers looking to address a spike in gun violence that began in early summer 2020. Gun homicides drove the uptick.
Here's what you should know about ghost guns:

What ghost guns are

Ghost guns are untraceable, self-assembled firearms, often put together with parts sold online, sometimes in as little as 30 minutes.
The weapons, sometimes referred to by officials as "privately made firearms," or PMFs, do not have serial numbers, making them all the more difficult to track and regulate.
Purchasing kits to build ghost guns online does not require a background check, so buyers can sidestep the typical requirements that might come with buying a firearm.
This means anyone -- no matter their age or criminal record -- can buy the kits and assemble a weapon.

How prevalent they are

Calls for something to be done about ghost guns have grown as their use in shootings across the US has proliferated, with the weapons recovered at crime scenes in some big cities more frequently.
While ghost guns make up a relatively small percentage of the total number of guns recovered by law enforcement, officials in several cities have reported sharp increases in those tallies, a CNN analysis of 2021 data found.
In San Francisco, for example, about 20% of the nearly 1,100 guns it seized in 2021 were ghost guns, police there told CNN.
And New York is on pace to again shatter the previous year's total, according to data shared with CNN. Since the start of this year, the NYPD has recovered 163 ghost guns, compared to 29 over the same period in 2021, mayor Eric Adams said Monday.
In 2021, New York authorities seized 4,497 firearms -- 375, or 8.33%, were ghost guns.
Of the 12,088 guns recovered in Chicago last year, 455, or 3.76%, were ghost guns, according to data from the city, up from 130 ghost guns recovered in 2020, when ghost guns made up 1.15% of the 11,343 guns recovered.
Between 2016 and 2021, the ATF received 45,000 reports of privately made firearms recovered by law enforcement in criminal investigations, including 20,000 reported last year alone. The agency was able to trace only 1% of the 45,000, officials said, because the firearms lack serial numbers.
The number of guns the ATF traced rose from about 217,000 in 2015 to just over 393,000 in 2020.
Just this past week, a ghost gun was recovered outside the home of a suspect arrested for the fatal shooting of a 16-year-old girl in the South Bronx, a police source told CNN.

What Biden announced

The regulation the Biden administration announced Monday addresses a gap in the government's ability to track ghost guns, requiring background checks before kit purchases and inclusion of serial numbers on some pieces used to assemble weapons.
"The Biden administration is making sure these kits are treated as the deadly firearms they are," a senior administration official said ahead of the announcement.
The new rules require anyone purchasing a kit to undergo a background check, which is required for other kinds of firearm purchases. Those selling kits will also be required to include a serial number on the components that make up the weapon, so the eventual firearm can be traced.
Additionally, the new rules mandate firearm dealers add a serial number to already-assembled ghost guns they come across.
"It's no longer a ghost," Biden said in the Rose Garden on Monday. "It has a return address. And it's going to help save lives, reduce crime and get more criminals off the streets."

What steps states have taken

At least 10 states and Washington, DC, have already taken steps to restrict or ban the purchase or use of ghost guns, according to the Giffords Law Center to Prevent Gun Violence.
Maryland was the latest to join last week, when the governor allowed legislation to pass that altered the definition of "firearm" to include an unfinished frame or receiver and prohibiting the sale of such components, among other steps.
Republican Gov. Larry Hogan thanked the legislature for addressing untraceable firearms in a letter. But he said the legislation did not go far enough to hold accountable those who actually commit shootings.
Last October, New York Gov. Kathy Hochul, a Democrat, signed legislation last October aimed at tackling the epidemic of gun violence, including prohibiting "the sale of ghost guns and requiring gunsmiths and dealers in firearms to register firearms in their possession," according to the governor's office.

Federal cases have targeted alleged traffickers

In the meantime, federal authorities have been cracking down on those who are either in posses