In his first televised interview as president-elect, Donald Trump gave a glimpse into his plans for large-scale deportations. He suggested his administration would initially target 2-3 million undocumented immigrants for removal, people who he branded criminals, “gang members, drugs dealers”. But even a cursory analysis of Trump’s target number of deportations shows that he will have to deport far more than undocumented immigrants convicted of serious crimes.

The incoming Trump administration will try to implement the harshest immigration regime in presidential history, with his closest advisers making clear they will seek to expedite these deportations. And those deported are likely to include a far greater number of those who have lived in the US for years – perhaps, experts warn, even those who are in the US on temporary visas or green cards.

The US already deports vast numbers of undocumented immigrants. During the first six years of his tenure, Barack Obama deported two and a half million people, under the guise of ridding the US of “criminals, gang bangers, [and] people who are hurting the community”. Obama’s rhetoric was somewhat misleading – a New York Times investigation found that two-thirds of those deported by the administration by 2013 had only minor criminal convictions or none at all. This underlies the impossibility of Trump’s pledge: there simply are not enough people who match his description as serious criminals to deport, and many speculate the targets he wants to reach will mean not only dramatically broadening the scope of deportations to meet targets, but also seriously curtail any oversight within the system.

“It’s important to point out that Obama was actively trying to deport a record number of people, and even he hit two and a half million over two terms,” said Grace Meng, a senior immigration researcher at Human Rights Watch’s US program. “So the idea of 2 to 3 million, whether it’s immediately, or even within a couple of years, would require a system that really defies our imagination of what a fair system might be.”

In the absence of official data, the Migration Policy Institute estimates about 820,000 of the roughly 11 million undocumented migrants living in America are likely to have a criminal conviction, with only 300,000 projected to hold a felony conviction. Since November 2014, the Obama administration has actively targeted this cohort of individuals. They have drastically reduced the number of interior deportations – those involving apprehensions that occur away from the border and usually involve individuals who have lived in the US for years – by activating a “Priority Enforcement Program”. This program sees Immigration and Customs Enforcement [Ice] agents prioritise undocumented arrestees picked up by state or local law enforcement who are found to have serious felonies, gang affiliations or terror suspicions.

But even under this new policy, Ice data obtained under the Freedom of Information Act by researchers at the University of Iowa, and reported here for the first time, highlights that a tiny fraction – 6.73% of total deportations in 2014 – involved individuals convicted of a violent crime, while 43.5% were deported with no recorded criminal history at all.

To get to 2 to 3 million will mean a dramatic rewriting of who or what is a criminal Professor Karthick Ramakrishnan, UC Riverside

“To get to 2 to 3 million [deportations] will mean a dramatic rewriting of who or what is a criminal, and rewriting that definition in a way that involves acts most Americans would not consider to be a crime,” said Professor Karthick Ramakrishnan, an immigration researcher at the University of California, Riverside and author of Framing Immigrants. “It would also mean considering not just undocumented immigrants, but people here who are on temporary visas or green cards that have committed minor crimes like shoplifting or DUI.”

Trump’s advisers have now acknowledged their net will need to widen and have started explaining that the administration will seek to deport not just convicted criminals but also those accused of a crime or gang affiliation as well as those charged with minor immigration violations, such as illegal re-entry.

Some have argued that Trump’s new immigration regime could simply use the tools left over from the so-called deportation machines created by both the Bush and Obama administrations. But the sheer scale of Trump’s project and the perceived desire to act quickly will probably require legislative action through Congress to enhance and expand the effectiveness of these devices.

In August, Trump pledged to restore the Secure Communities program, the precursor to the Priority Enforcement Program, which was utilised by both the Bush and Obama administration until 2014. The program allowed federal authorities to conduct broader, less targeted sweeps of undocumented arrestees held by local authorities, and allowed Ice agents to request that local jails detain suspects past their release date in order to allow more time to transfer them to federal detention facilities.

In the same speech, Trump also pledged to expand 287(g) agreements between Ice and local law enforcement, which allow local police officers to carry out certain functions of immigration law enforcement directly. Ice reportedly credited these partnerships with identifying more than 400,000 “potentially removable aliens” between 2006 and 2015, according to Politifact. But local law enforcement officials, most notably the Maricopa County sheriff’s office in Arizona, were routinely criticized for discriminatory policing, and as a result the Obama administration substantially rolled back their use in 2012.

Trump’s promise to expand or reinstate both these programs is a strong indication the new administration will significantly intensify interior deportations. But these removals have markedly declined since Obama entered office, from 237,941 in 2009 to 69,478 last year, as the outgoing administration – particularly in its second term – focused on deportations at the border, many of which occur through an expedited removal process that requires no hearing in court.

This sharpening of the interior deportation machine will leave a number of institutions in the crosshairs for reform, said conservative analysts close to Trump’s transition team. First, the Trump administration will probably focus on “streamlining” civil immigration proceedings in court, said Dan Stein, president of the Federation for American Immigration Reform (Fair).

“The different kinds of changes that would be made in the court system will include dramatically adding to the number of immigration judges, curtailing review opportunities, hopefully making some changes to the board of immigration appeals, and really suggesting to Congress that they limit the definition of asylum,” said Stein, whose organisation is listed as an anti-immigrant extremist group by the Southern Poverty Law Center.

There is already a backlog of over half a million cases before the immigration courts, making this task nothing short of monumental, and leaving advocates concerned that due process could simply fly out of the window.

Stein also predicted the Trump administration will seek to expand the Ice detention network, due to the rising rate of interior apprehensions. The network already detains more than 30,000 people and relies heavily on privatised, substandard facilities, raising concerns that the standard of care will plummet even further.

But to proceed with even just these two reforms, the Trump administration will probably need significant funding passed through Congress. For some advocates there is hope that this may at least curtail Trump’s ability to act with the pace he seems wedded to.

“Anything that needs to be done by Congress is going to take time and I think there are Republican and Democratic members in Congress who see immigrant rights as being crucial to the wellbeing of this country, and I hope they will resist these efforts,” said Meng, of Human Rights Watch. “It’s already a very expensive system.”