The first misleading statement in President Donald Trump's Oval Office address on Tuesday night came in the first sentence.

Mr Trump, addressing a national television audience from behind his desk, warned of a "security crisis at the southern border" - even though the number of people caught trying to cross illegally is near 20-year lows.

Another false claim came moments later, when Mr Trump said border agents "encounter thousands of illegal immigrants trying to enter our country" every day, though his administration puts the daily average for 2018 in the hundreds. A few sentences later, he said 90 per cent of the heroin in the United States comes across the border with Mexico, ignoring the fact that most of the drugs come through legal entry points and would not be stopped by the border wall he is demanding as the centrepiece of his showdown with Democrats.

Over the course of his nine-minute speech, Mr Trump painted a misleading and bleak picture of the situation at the US-Mexico border. He pumped up some numbers, exaggerated the public safety risks of immigration and repeated false claims regarding how to fund a border wall.

The appearance, coming as a partial federal government shutdown resulting from the wall fight enters its third week, underscored the extent to which Mr Trump has relied on false and misleading claims to justify what has long been his signature political issue.

One false claim noticeably absent from the speech was the assertion made by the president and many of his allies in recent days that terrorists are infiltrating the country by way of the southern border. Fact-checkers and TV anchors, including those on Fox News, spent days challenging the truthfulness of the claim.

Below are the truths behind Mr Trump's claims from the Oval Office address:

"Tonight I am speaking to you because there is a growing humanitarian and security crisis at our southern border."

By any available measure, there is no new security crisis at the border.

Apprehensions of people trying to cross the southern border peaked most recently at 1.6 million in 2000 and have been in decline since, falling to just under 400,000 in fiscal 2018. The fall is partly because of technology upgrades; tougher penalties in the wake of the 9/11 terrorist attacks; a decline in migration rates from Mexico; and a sharp rise in the number of Border Patrol officers. The fiscal 2018 number was up from just over 300,000 apprehensions at the US-Mexico border for fiscal 2017, the lowest level in more than 45 years.

There are far more cases of travellers overstaying their visas than southern border apprehensions. In fiscal 2017, the Department of Homeland Security reported 606,926 suspected in-country overstays, or twice the number of southern border apprehensions. In fiscal 2016, US officials reported 408,870 southern border apprehensions and 544,676 suspected in-country overstays.

While overall numbers of migrants crossing illegally are down, since 2014, more families from El Salvador, Guatemala and Honduras began to trek to the United States in search of safer conditions or economic opportunities, creating a humanitarian crisis.

"Record numbers of migrant families are streaming into the United States, overwhelming border agents and leaving holding cells dangerously overcrowded with children, many of whom are falling sick," The Washington Post reported on 5 January. "Two Guatemalan children taken into US custody died in December."

President Trump makes televised plea for border wall funding as he declared there is 'a humanitarian crisis'

"Every day Customs and Border Patrol agents encounter thousands of illegal immigrants trying to enter our country."

Southern border apprehensions in fiscal 2018 averaged 30,000 a month (or 1,000 a day). They ticked up in the first two months of fiscal 2019, but it is a stretch to say "thousands" a day. Better to say "hundreds."

"America proudly welcomes millions of lawful immigrants who enrich our society and contribute to our nation, but all Americans are hurt by uncontrolled illegal migration. It strains public resources and drives down jobs and wages. Among those hardest hit are African-Americans and Hispanic-Americans."

Some context here: In general, economists say illegal immigration tends to affect less-educated and low-skilled American workers the most, which disproportionately encompasses black men and recently arrived, low-educated legal immigrants, including Latinos.

The US Commission on Civil Rights in 2010 found illegal immigration has tended to depress wages and employment for black men. However, there are other factors at play, and "halting illegal immigration is not a panacea even for the problem of depressed wage rates for low-skilled jobs," it found.

The consensus among economic research studies is that the impact of immigration is primarily a net positive for the US economy and to workers overall, especially over the long term. According to a comprehensive 2016 report by National Academies of Sciences, Engineering, and Medicine on the economic impacts of the US immigration system, studies on the impact of immigration showed "the seemingly paradoxical result that although larger immigration flows may generate higher rates of unemployment in some sectors, overall, the rate of unemployment for native workers declines."

"Our southern border is a pipeline for vast quantities of illegal drugs, including meth, heroin, cocaine, and fentanyl. Every week, 300 of our citizens are killed by heroin alone, 90 per cent of which floods across from our southern border."

In 2017, more than 15,000 people died of drug overdoses involving heroin in the United States, according to the Centers for Disease Control and Prevention. That works out to about 300 a week.

But while 90 per cent of the heroin sold in the United States comes from Mexico, virtually all of it comes through legal points of entry. "A small percentage of all heroin seized by CBP along the land border was between Ports of Entry (POEs)," the Drug Enforcement Administration said in a 2018 report. So Mr Trump's wall would do little to halt drug trafficking. Mr Trump's repeated claim that the wall would stop drug trafficking is one of his more dubious.

Miguel Saavedra (L) and his friend Oswaldo Hernandez (C) watch President Trump on TV from their home in Miami, Florida (EPA)

"In the last two years, ICE officers made 266,000 arrests of aliens with criminal records, including those charged or convicted of 100,000 assaults, 30,000 sex crimes, and 4,000 violent killings. Over the years, thousands of Americans have been brutally killed by those who illegally entered our country, and thousands more lives will be lost if we don't act right now."

Mr Trump warns about dangerous criminals, but the numbers he is citing involve a mix of serious and non-violent offences such as immigration violations. US Immigration and Customs Enforcement reports yearly arrest totals without breaking down the type of offence, which could be anything from homicide to a DUI to illegal entry.

Notice how Mr Trump switches quickly from the 266,000 arrests over two years to charges and convictions: "100,000 assaults, 30,000 sex crimes, and 4,000 violent killings." In many cases, the people arrested face multiple counts, so that switch gives a confusing picture.

In fiscal 2018, ICE conducted 158,581 administrative arrests for civil immigration violations. The agency's year-end report says two-thirds (105,140) of those involved people with criminal convictions and one-fifth (32,977) involved people with pending criminal charges. Of the 143,470 administrative arrests in 2017, 74 per cent involved people with criminal records and 15.5 per cent who had pending charges. But these totals cover all types of offences - including illegal entry or re-entry.

In the fiscal 2018 breakdown, 16 per cent of all the charges and convictions were immigration and related offences.

"Last month, 20,000 migrant children were illegally brought into the United States, a dramatic increase. These children are used as human pawns by vicious coyotes and ruthless gangs."

No government statistic tracks children smuggled in by bad actors, "coyotes" or "drug gangs." What Mr Trump is referring to is CBP's number for family unit apprehensions, a monthly statistic. The family unit by definition must include at least one parent or legal guardian and one minor. (There is a separate figure for unaccompanied alien children.)

That number was 25,172 in November, the most recent month for which data are available, but it is wrong to describe it as a statistic that represents children being "smuggled" into the country.

Mr Trump describes this as 20,000 children, but it could be many more considering that some families have multiple children. More important, Mr Trump describes this as children being smuggled in by coyotes or drug gangs, but border officials screen for false claims of parentage. To imply as Mr Trump does that a child's mother, father or legal guardian is a smuggler, coyote or drug gang member in all of these cases is wrong.

Who could be running against Trump in 2020? Show all 23 1 /23 Who could be running against Trump in 2020? Who could be running against Trump in 2020? Joe Biden The former vice president - poised to be a frontrunner - has announced his run. He recently faced scrutiny for inappropriate touching of women, but was thought to deal with the criticism well AFP/Getty Who could be running against Trump in 2020? Bernie Sanders The 2016 runner-up has announced that he will be running again in 2020 Getty Who could be running against Trump in 2020? Hillary Clinton The 2016 Democratic presidential candidate and former Secretary of State says she is “still considering” whether she will run again. Getty Who could be running against Trump in 2020? Pete Buttigieg The Indiana mayor and war veteran will be running for president. If elected, he would be the first openly LGBT+ president in American history. Getty Who could be running against Trump in 2020? Kamala Harris The former California attorney general will be running for president in 2020. Introduced to the national stage during Jeff Sessions’ testimony, she has endorsed Medicare-for-all and proposed a major tax-credit for the middle class. AP Who could be running against Trump in 2020? Elizabeth Warren The Massachusetts Senator has formally launched her bid for president in 2020. A progressive Democrat, she is a major supporter of regulating Wall Street. AP Who could be running against Trump in 2020? Beto O’Rourke The former Texas congressman told Oprah Winfrey that he “has been thinking about running for presidency”, but stopped short of formally announcing his bid to run in 2020. AFP/Getty Who could be running against Trump in 2020? Wayne Messam Mayor of the city of Miramar in the Miami metropolitan area, Wayne Messam has announced his bid. He intends to run on a progressive platform against the "broken" federal government. He favours gun regulations and was a signatory to a letter from some 400 mayors condemning President Trump's withdrawal from the Paris Climate Accord. Vice News Who could be running against Trump in 2020? Kirsten Gillibrand The New York Senator formally announced her presidential bid in January, saying that “healthcare should be a right, not a privilege.” Getty Who could be running against Trump in 2020? Cory Booker The New Jersey Senator has announced that he will be running for the presidency in 2020. If he secures the nomination he said finding a female vice president would be a priority. Getty Who could be running against Trump in 2020? John Delaney The Maryland congressman was the first to launch his bid for presidency, making the announcement in 2017. AP Who could be running against Trump in 2020? Julian Castro The former San Antonio mayor announced his candidacy in January and said that his running has a “special meaning” for the Latino community in the US. Getty Who could be running against Trump in 2020? Tulsi Gabbard The Hawaii congresswoman announced her candidacy in January, but is likely to face tough questions on her past comments on LGBT+ rights and her stance on Syrian President Bashar al-Assad. Getty Who could be running against Trump in 2020? Andrew Yang The entrepreneur has announced his presidential candidacy, and has pledged that he would introduce a universal basic income of $1,000 a month to every American over the age of 18. AFP/Getty Who could be running against Trump in 2020? Marianne Williamson The author and spiritual advisor has announced her intention to run for president. She had previously run for congress as an independent in 2014 but was unsuccessful. Getty Who could be running against Trump in 2020? John Kerry The former secretary of state has said he is still thinking about whether to run. Getty Who could be running against Trump in 2020? Michael Bloomberg The entrepreneur and former New York mayor– with a net worth of around $50bn – has said he will decide by the end of February whether to seek the presidency. AFP Who could be running against Trump in 2020? Howard Schultz Former Starbucks CEO Howard Schultz has not yet ruled out running for president in 2020, despite criticism that his bid could help re-elect Mr Trump by dividing the Democrat vote. AP Who could be running against Trump in 2020? Eric Holder The former attorney general has said he will decide in “the next month or so” whether to run as a 2020 presidential candidate. AP Who could be running against Trump in 2020? Eric Swalwell The California congressman said he is “ready to do this” and will decide before April whether to run. MSNBC Who could be running against Trump in 2020? Terry McAuliffe The former Virginia governor, who worked to elect Democratic governors during 2018 midterms, said there was a “50 per cent” chance he would run. AP Who could be running against Trump in 2020? Sherrod Brown The Ohio senator is still undecided about whether to run for president in 2020. Who could be running against Trump in 2020? Mitch Landrieu The former New Orleans mayor said he doesn’t think he will run for president, but “never say never”. AP Photo/Jacquelyn Martin

"Furthermore, we have asked Congress to close border security loopholes so that illegal immigrant children can be safely and humanely returned back home."

The Trump administration considers the Flores settlement agreement a loophole. That policy requires the government to release unaccompanied immigrant children who are caught crossing the border within 20 days to shelters, family members or "least restrictive" settings.

The president also wants to tighten US asylum laws generally and the Trafficking Victims Protection Reauthorisation Act, with the goal of restricting some immigrants' opportunities to file asylum petitions. Mr Trump describes these asylum provisions as "border security loopholes," but supporters call them core provisions of US laws that cover refugees.

"Finally, as part of an overall approach to border security, law enforcement professionals have requested $5.7 billion for a physical barrier. At the request of Democrats, it will be a steel barrier rather than a concrete wall."

Mr Trump suggests Democrats requested a steel barrier rather than a concrete wall, but the proposed switch to steel was an idea the Trump administration brought up. No Democrats are on record demanding a steel barrier along the US-Mexico border.

"This is just common sense. The border wall would very quickly pay for itself. The cost of illegal drugs exceeds $500 billion a year, vastly more than the $5.7 billion we have requested from Congress."

Mr Trump tweeted a similar claim in March, citing a study from the Centre for Immigration Studies, which supports more restrictive immigration policies. Essentially, the claim that the wall pays for itself turns on three numbers: a) estimated savings from each undocumented immigrant blocked by the wall, b) the total number of undocumented immigrants stopped over 10 years, and c) the cost of the wall.

It is (a) $75,000 multiplied by (b) 160,000 to 200,000 equals (c) $12 billion to $15 billion. So, if the wall actually costs $25 billion, the number of undocumented immigrants halted by the wall would need to be doubled, or one has to assume it would take 20 years to earn the money back. But other experts offer different estimates for each of those numbers.

Plus, as we have previously reported, the wall would do little to stop drugs from entering the United States, since they primarily come in through legal points of entry, making the cost of illegal drugs irrelevant to this issue.

"The wall will also be paid for indirectly by the great new trade deal we have made with Mexico."

This is a Four Pinocchio claim. During the campaign, Mr Trump promised more than 200 times Mexico would pay for the wall, which the administration says would cost at least $18 billion. Now, he says a minor reworking of the North American Free Trade Agreement (NAFTA) will earn enough money to pay for the wall.

This betrays a misunderstanding of economics. Countries do not "lose" money on trade deficits, so there is no money to earn; the size of a trade deficit or surplus can be determined by other factors besides trade. Congress must still appropriate the money, and the trade agreement has not been ratified.

"Senator Chuck Schumer, who you will be hearing from later tonight, has repeatedly supported a physical barrier in the past, along with many other Democrats. They changed their mind only after I was elected president."

Mr Schumer, Hillary Clinton and many other Democrats voted for the Secure Fence Act of 2006, which authorised building a fence along nearly 700 miles of the border between the United States and Mexico. But the fence they voted for is not as substantial as the wall Mr Trump is proposing. Mr Trump himself has called the 2006 fence a "nothing wall."