WITH MARIA HINOJOSA, SCOTT SIMON, RAY SUAREZ AND THIS WEE JEFF GREENFIELD.

ON THIS EDITION, MANY HAVE AMERICAN CHILDREN, HOLD AMERICAN JOBS AND PAY AMERICAN TAXES -- >> THEY'RE LOOKING OUT FOR THEIR FAMILIES, THEY'RE LOOKING OU FOR THEIR NEIGHBORS.

THEY ARE WOVEN INTO THE FABRIC OF OUR LIVES >> Announcer: BUT EVEN A CONGRESS INCHES CLOSER TO A DEAL THAT COULD INCLUDE A PATHWAY T CITIZENSHIP FOR 11 MILLION UNDOCUMENTED WORKERS, A GROWIN NUMBER OF THEM ARE STILL BEING DEPORTED, AND MANY ARE DYING WHEN THEY TRY TO RETURN.

>> HE CALLED US AND TOLD US WHEN YOUR DAD WAS DYING THE ONL THING HE WAS SAYING WAS "I DON'T WANT TO DIE.

I DON'T WANT TO DIE.

I WANT GO BACK TO MY KIDS.

>> Announcer: NEXT ON "NEED TO KNOW."

>> WELCOME TO "NEED TO KNOW.

THANKS FOR JOINING US.

YOU'VE PROBABLY HEARD THAT ILLEGAL IMMIGRATION INTO THE UNITED STATES FROM MEXICO HA SLOWED DRAMATICALLY IN RECEN YEARS.

SOME ATTRIBUTE THAT TO BETTE BORDER SECURITY.

OTHERS SAY IT'S ALL ABOUT JOBS THERE JUST AREN'T AS MANY JOBS AS THERE USED TO BE IN THE UNITED STATES.

WHATEVER THE CAUSE, THE TREND IS UNMISTAKABLE WHICH MAKES ANOTHER TREND EVEN MORE NOTEWORTHY.

EVEN AS ILLEGAL CROSSING DECLINE, THE NUMBER OF DEATH ALONG THE BORDER IS SOARING.

WHAT'S BEHIND THAT TREND THIS WEEK, PART THREE OF "NEED TO KNOW'S" ONGOING INVESTIGATION INTO OUR BORDER POLICIES AND PROCEDURES, DONE IN CONJUNCTIO WITH THE NATION INSTITUTE.

JOHN LARSON INVESTIGATES >> ON THE REMAINS WE HAD SOM U.S. CURRENCY, THIS CROSS HERE IS FAIRLY DISTINCTIVE.

>> Reporter: YOU'RE LOOKING AT >> Reporter: YOU'RE LOOKING AT THE PERSONAL BELONGINGS OF A MAN KNOWN TO THE STATE OF ARIZONA AS CASE 1,555 >> WE HAVE A SANTA MUERTE HERE WE HAVE A COUPLE OF NECKLACES.

>> Reporter: IN THE LOCKED FILES, THOUSANDS OF ITEM BELONGING TO HUNDREDS OF PEOPLE, ALL OF WHOM WERE FOUND DEAD.

IN MORTUARIES AND COUNTY OFFICES FROM TEXAS TO CALIFORNIA, LA UNIDENTIFIED REMAINS OF PEOPLE WHO CROSSED INTO THE UNITE STATES ILLEGALLY ONLY TO BECOM FOOTNOTES IN THE MOST LETHAL CHAPTER IN RECENT U.S. IMMIGRATION HISTORY.

>> THIS IS OUR INDOOR COOLER >> Reporter: SILENT PARTICIPANTS IN THE NATIONAL DEBATE O IMMIGRATION REFORM >> THIS COOLER HOLDS UP TO 120 REMAINS.

>> Reporter: BECAUSE EVEN AS THE ADMINISTRATION SUPPORTS POSSIBLE PATHWAY TO CITIZENSHI FOR MANY OF THE NATION'S 1 MILLION UNDOCUMENTED IMMIGRANTS, MANY OF THOSE SAME PEOPLE AR NOW BEING ROUNDED UP, DEPORTED IN RECORD NUMBERS, AND ARE DYING AT A HISTORIC RATE TRYING TO GET BACK TO THEIR FAMILIES I AMERICA.

>> I JUST WANTED TO SAY GOOD-BYE TO HIM I WANTED TO SAY SOMETHING.

>> Reporter: THE PRESIDENT HAS HIT THE ROAD TO SELL IMMIGRATION REFORM TO THE PUBLIC >> FOR COMPREHENSIVE IMMIGRATION REFORM TO WORK, IT MUST BE CLEAR FROM THE OUTSET THAT THERE IS PATHWAY TO CITIZENSHIP >> Reporter: AND YET BY THE EN OF THIS YEAR, OBAMA WILL HAV PRESIDED OVER MORE ARRESTS AND DEPORTATIONS THAN ANY AMERICAN PRESIDENT.

2 MILLION PEOPLE IN 5 YEARS, MANY THE SAME PEOPLE HE SAYS DESERVE TO BE CITIZENS INCLUDING SOME WHO WIND UP HERE.

>> SO THIS IS 2012 CASE NUMBER 2,637.

>> Reporter: WHEN DR. GREG HES WAS A MEDICAL EXAMINER I MILWAUKEE, WISCONSIN, ONE YEAR HE HAD JUST ONE, UNIDENTIFIE BODY AS MEDICAL EXAMINER HERE IN PIMA COUNTY, ARIZONA, HE'S HAD OVER 2,000.

BACK IN THE 1990s WHEN ILLEGAL IMMIGRATION WAS HIGH, THE NUMBER OF MIGRANTS DYING IN THE ARIZONA DESERT WAS LOW, LITERALLY JUST A HANDFUL.

>> BUT YOU CAN SEE HERE, I CAN ALMOST GRAB WITH ONE HAND TH UNIDENTIFIED REMAINS FROM TH '90s THEN ALL OF A SUDDEN WE GE 2000, 2001, 2002, AND ALL THES ARE FROM THE 2000s >> Reporter: WHAT HAPPENED WHY MORE THAN 2,500 MIGRANTS HAVE NOW DIED IN ARIZONA ALONE SINCE THE YEAR 2000 MAY HAVE A LOT TO DO WITH A RELATIVEL RECENT CHANGE IN U.S IMMIGRATION POLICY, A CHANGE CALLED PREVENTION THROUGH DETERRENC WHICH BEGAN IN 1994.

>> THE DETERRENT STRATEGY BEGA AS JUST A BASIC RESPONSE T WHERE TRAFFIC WAS HAPPENING, ILLEGAL ACTIVITY >> Reporter: THAD BINGEL WAS THE CHIEF OF STAFF FOR U.S CUSTOMS AND BORDER PROTECTIO FROM 2007 TO 2009.

HE SAYS IN THE '80s AND '90s ILLEGAL IMMIGRANTS CAME IN WAVES, MOSTLY IN URBAN AREAS WITH FEW FENCES TO STOP THEM >> AT THAT TIME YOU LITERALLY, DOZENS OF PEOPLE A DAY JUST YO KNOW WHERE YOU COULD SEE THEM IN GROUPS RUNNING ACROSS THE BORDER IN SAN DIEGO THERE WASN'T FENCE THERE >> Reporter: BUT THAT QUICKL CHANGED.

THE U.S. GOVERNMENT NOW PATROL 651 MILES OF FENCE, SPENDING OVER $11 BILLION A YEAR ON INCREASED BORDER SECURITY.

AND IN SOME WAYS IT WORKED FEWER PEOPLE NOW CROSS ILLEGALLY.

BUT THE STRATEGY WAS NOT JUST TO KEEP PEOPLE OUT, BUT TO FUNNEL THOSE WHO MADE IT ACROSS THE BORDER INTO THE DESERT, INTO "MORE HOSTILE TERRAINE, LESS SUITED FOR CROSSING AND MORE SUITED FOR ENFORCEMENT," WHERE THEY MIGHT BE EASIER TO CATCH.

AS A U.S. BORDER PATROL VIDE SHOWN TO THE PUBLIC IN 2009 PU IT - >> WE NOW HAVE THE TACTICA ADVANTAGE AND WE ONLY NEED T EXPLOIT THAT ADVANTAGE >> Reporter: WHILE THE GOAL MA HAVE BEEN TO MAKE IT EASIER TO CATCH ILLEGAL IMMIGRANTS, IT HAD AN UNINTENDED CONSEQUENCE.

MANY MORE OF THOSE CROSSING AR DYING.

>> THE TEMPERATURE IS GETTIN REALLY BAD >> Reporter: WE JOINED A GROUP OF VOLUNTEERS, AND THIS AMERICAN MOTHER, IN A SEARCH FOR HE HUSBAND IN THE ARIZONA DESERT.

HER HUSBAND WAS DEPORTED FRO THE U.S. AND WAS LOST TRYING T RE-ENTER THE COUNTRY ILLEGALLY HE WAS TRAVELLING THE SO-CALLE "DEVIL'S HIGHWAY," A TANGLED WEB OF TRAILS LEADING NORTH FROM MEXICO TO ARIZONA AND INTO THI VALLEY WHERE TEMPERATURES CA REACH 120 DEGREES, AND THE DESERT IS FILLED WITH SNAKES SCORPIONS AND SMUGGLERS.

IT IS LITERALLY A VALLEY O DEATH, THE MAP SHOWING WHERE THE BODIES OF MIGRANTS HAVE BEEN FOUND.

CECILIA'S HUSBAND HAD BEEN ABANDONED BY HIS TRAVELING COMPANIONS, AND WAS DELIRIOU ON HIS CELL PHONE.

IT WAS THE LAST TIME THE TALKED >> AND I SAID THAT I LOVED HIM AND HE WAS LIKE I LOVE YOU AND THE BABY IT WAS REALLY HARD >> Reporter: TWO MONTHS AFTE THAT FINAL CALL, SHE STILL PAY HIS CELL PHONE BILLS, HOPING HE'LL CALL AGAIN >> AND I DIDN'T HEAR ANYTHIN FROM HIM SINCE >> Reporter: ON ANOTHER SEARCH IN TEXAS, WE GOT A FIRSTHAND LESSON JUST HOW QUICKLY TH DESERT MIGHT TAKE A LIFE >> THIS WOMAN IS A AMERICAN CITIZEN SHE HAD BEEN SEARCHING FOR HER NEPHEW, WHO HAD DECIDED TO ENTER THE COUNTRY ILLEGALLY.

DURING THE SEARCH, SHE WAS OVERCOME BY THE HEAT DESPITE FLUIDS AND SHADE, HE SYMPTOMS ESCALATE.

[ SPEAKING SPANISH ] >> Reporter: SHE WOULD EVENTUALLY RECOVER THE NEXT DAY, HOWEVER, SHE WOULD FIND HER NEPHEW'S BODY IN LOCAL MORGUE ACROSS THE SOUTHWEST, HUNDREDS OF UNIDENTIFIED MIGRANTS ARE BURIED IN LOCAL CEMETERIES WITHOUT NAMES.

OTHERS ARE BURIED IN CEMETERIE FOR THE UNKNOWN, AMONG THE QUIETEST PLACES IMAGINABLE >> SO WHAT DO WE KNOW ABOU PEOPLE DYING ON THE BORDER >> Reporter: ANDREW LEHREN, REPORTER FOR "THE NEW YORK TIMES," TEACHES GRADUATE INVESTIGATIVE JOURNALISM IN NE YORK AT OUR REQUEST, HIS STUDENTS SEARCHED THOUSANDS OF MEXICA AND U.S. GOVERNMENT FILES, DEATH RECORDS IN COUNTIES ALL ALON THE BORDER, AND MADE TWO STARTLING OBSERVATIONS -- ONE, THAT WHILE THE NUMBER OF ILLEGAL CROSSINGS HAS PLUMMETED, ALMOS 80% LESS THAN IN PEAK YEARS, THE NUMBER OF DEATHS HAS ACTUALL INCREASED.

MEANING THAT FOR THOSE COMIN INTO THE COUNTRY, IT IS NOW MORE DEADLY, MORE LETHAL, THAN AT ANY TIME IN RECENT U.S. IMMIGRATIO HISTORY.

SO YOUR CHANCES OF DYING CROSSING THE BORDER AS A ILLEGAL ARE GREATER NOW THAN THEY WERE SAY TEN YEARS AGO?

>> THAT'S WHAT THE DATA AN REPORTS SEEM TO SHOW >> Reporter: AND, THAT FOR YEARS THE AGE OF THOSE DYING HAS BEE CONSTANT, THEY HAVE BEEN YOUNG BUT FOR UNKNOWN REASONS, NOT ANYMORE.

>> TEN YEARS AGO THEY WERE I THEIR LATE 20s UP TO LIK MAYBE 30 AND NOW THE AVERAGE AGE IS MORE AROUND 34.

>> THE THING WE DON'T KNOW I WHAT'S COMPELLING PEOPLE T CROSS THE BORDER PARTICULARLY PEOPLE GETTIN OLDER.

>> Reporter: WHAT MAY BE COMPELLING OLDER IMMIGRANTS TO RISK DEATH IN THE DESERT I THIS, MORE AND MORE OFTEN, THE ARE MOTHERS AND FATHERS WHO HAVE LONG HAD HOMES IN THE UNITED STATES, WITH AMERICAN CHILDREN WHO DEPEND ON THEM WHY THE SHIFT?

SINCE 2009, THE OBAM ADMINISTRATION HAS EXPANDED BUSH ADMINISTRATION POLICY EMPOWERING LOCAL POLICE TO HEL THE DEPARTMENT OF HOMELAND SECURITY ARREST UNDOCUMENTED WORKERS.

>> YOU'RE UNDER ARREST FOR N DRIVER'S LICENSE >> Reporter: CALLED "SECUR COMMUNITIES," THE PROGRAM IS RESPONSIBLE FOR MANY DEPORTATIONS BUT MOST ARRESTS WERE NOT ON THE BORDER, BUT IN THE INTERIOR, SWEEPING UP PEOPLE WHO EVEN SOME OF THE PRESIDENT'S CRITICS NOW BELIEVE SHOULD BE ELIGIBLE FOR CITIZENSHIP.

>> MOST OF THESE PEOPLE HAVE BEEN HERE FOR MORE THAN DECADE THEY HAVE CHILDREN THAT ARE U.S. CITIZENS, THEY MAY EVEN OW PROPERTY, THEY WORK.

THEY'RE HERE AND THEY'RE NEVER GOING TO GO BACK >> THESE ARE PEOPLE THAT ACTUALLY HAVE A LOT OF CONNECTIONS TO THE U.S. AND THIS HAS INCREASED DRAMATICALLY EVE OVER THE PAST THREE OR FOU YEARS.

>> Reporter: JEREMY SLACK, A DOCTORAL CANDIDATE AT TH UNIVERSITY OF ARIZONA, IS TH AUTHOR OF A NEW STUDY CALLED "IN THE SHADOW OF THE WALL."

STACK AND CO-WORKERS INTERVIEWED 1,100 DEPORTED MIGRANTS OVER FOUR YEARS AND LEARNED THOSE CAUGHT IN "SECURE COMMUNITIES" OPERATIONS MAY HAVE HELPED PUS DEPORTATIONS TO RECORD LEVELS, BUT WERE ALSO THE MOST LIKEL DEPORTEES TO COME RIGHT BACK >> AND SO ONE IN FOUR PEOPLE HAS AT LEAST ONE U.S. CITIZEN CHIL THAT'S UNDER THE AGE OF 18 AND THIS IS LARGELY ONE OF THE REASONS WHY YOU'RE SEEING SO MANY PEOPLE ATTEMPTING TO CROS DESPITE ALL THE DANGERS, O UNDOCUMENTED MIGRATION >> Reporter: WHICH BEGS TH QUESTION, WHY DON'T DEPORTEE JUST STAY IN MEXICO, BRING THEIR AMERICAN FAMILIES SOUTH, AND START OVER AGAIN IN MEXICO SLACK SAYS, SOME DO, BUT IT IS DIFFICULT FOR PEOPLE WITH LITTLE MONEY.

>> SO HOW DO YOU UPROOT YOUR FAMILY, GET RID OF ALL YOU STUFF, TAKE THEM OUT OF SCHOOL MOVE THEM BACK TO A PLACE IN MEXICO WHERE YOU DON'T NECESSARILY KNOW ANYONE, DON'T HAVE A JOB AND DON'T HAVE AN WAY TO SUPPORT THEM?

THIS BECOMES A REALLY DIFFICUL CHOICE >> Reporter: "NEED TO KNOW TRAVELED SOUTH TO NOGALES, A MEXICAN BORDER TOWN SOUTH OF ARIZONA, WHERE WE, FOUND DOZEN OF IMMIGRANTS FRESHLY DEPORTED FROM THE UNITED STATES WE ASKED HOW MANY HAD FAMILIES IN AMERICA, MOST EVERYONE IN THE ROOM RAISED THEIR HAND LISTEN TO ALMOST ANYONE HERE SEPARATED FROM THEIR CHILDREN IN AMERICA AND THEY'LL TELL YOU THEY ARE GOING BACK.

LIKE LEONARDO, A CONSTRUCTIO WORKER FROM NEVADA, WHO LIVE WITH HIS AMERICAN WIFE AND AMERICAN KIDS FOR TEN YEAR BEFORE BEING DEPORTED.

>> THEY TELL ME, "DADDY, I MIS YOU.

I WANT TO SEE YOU.

I LOVE YOU TOO MUCH.

I WANT TO SEE YOU.

>> Reporter: NOW, HE WILL TR CROSSING THE DESERT ALONE.

>> I DON'T WANT MY DAUGHTE GROWING UP WITHOUT ME.

THAT'S WHY I PUT MYSELF IN DANGER CROSSING THE DESERT >> Reporter: HOW THIS PLAYS OUT, WHILE DISCUSSIONS OF IMMIGRATION REFORM CONTINUE IN WASHINGTON, CAN BE ESPECIALLY PAINFUL FO THE AMERICAN FAMILIES, AND CHILDREN OF DEPORTEES.

>> MY MOM HAD SENT HIM TO GO GET MILK AND TORTILLAS >> Reporter: GLADYS DOMINGUEZ, IS THE 19-YEAR-OLD DAUGHTER OF ALFONSO MARTINEZ SANCHEZ, 39-YEAR-OLD FATHER OF FIVE AMERICAN CHILDREN, WHO HAD LIVED IN THE U.S. FOR MORE THAN 20 YEARS.

ONE DAY, ALFONSO WENT TO HIS NEIGHBORHOOD CONVENIENCE STORE IN VISTA, CALIFORNIA A COUNTY SHERIFF'S DEPUTY ASKE FOR HIS IDENTIFICATION, ARRESTED HIM, AND TURNED HIM OVER T FEDERAL IMMIGRATION AGENTS HIS WIFE JUANA ARRIVED WIT THEIR CHILDREN JUST IN TIME TO SEE HIM IN THE BACK OF A POLIC CAR, HANDCUFFED AND WEEPING.

>> I THINK HE WAS CRYING BECAUSE I BROUGHT MY KIDS AND HE WAS LOOKING OUT FROM INSIDE.

>> Reporter: HE WAS DEPORTED T MEXICO, WHERE HE MET THIS MAN.

>> Translator: ALFONZO WAS A LITTLE SHY HE WAS AFRAID OF TIJUANA, TO WALK AROUND ALONE ON THE STREE BECAUSE OF THE POLICE.

>> Reporter: ISAAC IS ALSO A UNDOCUMENTED WORKER IN THE UNITED STATES, AND LIKE ALFONSO, WAS ALSO TRYING TO GET BACK TO HIS WIFE AND AMERICAN CHILDREN IN CALIFORNIA.

THE TWO FATHERS BONDED QUICKLY AND DECIDED TO TRY SNEAK BAC ACROSS THE BORDER TOGETHER I KNOW THERE'S PEOPLE WHO MUST BE THINKING, YOUR FATHER'S BIG MISTAKE WAS THAT HE CAME TO TH COUNTRY ILLEGALLY.

YOU KNOW, IF HE HADN'T DON THAT, YOU'D ALL STILL BE TOGETHER >> WE HAVE NOTHING IN MEXICO WE DON'T HAVE A HOUSE, MY MO AND MY DAD HAVE BEEN HERE FO OVER 20 YEARS.

THEY DON'T KNOW ANYONE THERE WE DON'T KNOW ANYONE THERE >> Reporter: WHILE THERE IS NO QUESTION THAT SNEAKING BACK INTO THE UNITED STATES IS AGAINST THE LAW, BOTH MEN WOULD BE AMONG THE UNDOCUMENTED WORKERS CONSIDERE FOR CITIZENSHIP UNDER PENDIN LEGISLATION.

>> THEY'RE LOOKING OUT FOR THEIR FAMILIES THEY'RE LOOKING OUT FOR THEI NEIGHBORS.

THEY'RE WOVEN INTO THE FABRIC OF OUR LIVES.

>> Reporter: ALFONSO WORKED AS A BUTCHER, A LANDSCAPER, AND A CONSTRUCTION WORKER FOR NEARLY TWO DECADES.

ISAAC WORKED IN THE FIELDS BOTH WERE RAISING FAMILIES WHO DEPEND ON THEM OVER THE NEXT FE WEEKS, THEY TRY FOUR TIMES T RE-ENTER THE U.S EACH TIME, THEY ARE CAUGHT OR DETERRED BY U.S. BORDER PATROL WHEN THEY WERE CAUGHT THE FIRS TIME, ISAAC WAS SENT BACK TO TIJUANA.

ALFONSO WAS FLOWN 1,500 MILE AND RETURNED TO MEXICO IT'S A POLICY CALLED LATERAL DEPORTATION.

>> BORDER PATROL FOUND THAT IN INCIDENTS WHERE SOMEONE WA APPREHENDED AND PUT RIGHT BACK ACROSS CLOSE TO WHERE THEY WER APPREHENDED, THEY ALMOST IMMEDIATELY HOOKED UP WITH THE COYOTE OR SMUGGLER WHO HAD ATTEMPTED TO GET THEM ACROSS AND THEY WOULD MAKE REPEATED ATTEMPTS >> Reporter: MANY OF THOSE BEING LATERALLY DEPORTED, INCLUDIN ALFONSO, END UP IN MATAMOROS MEXICO, HOME TO ONE OF MEXICO' MOST BRUTAL CARTELS, INFAMOU FOR PREYING ON MIGRANTS STEALING THEIR MONEY, KIDNAPPING AN KILLING THEM IN 2010, 72 MIGRANTS WERE HAULED OFF A BUS ON THE WAY T MATAMOROS, AND MASSACRED LATER, BODIES OF ANOTHER 200 MIGRANTS WERE FOUND BURIED I MASS GRAVES.

>> THEY'VE BEEN KNOW TO PREY O MIGRANTS, ON DEPORTEES, AS A STREAM OF MONEY.

>> Reporter: JEREMY SLACK SAYS NOT ONLY DOES LATERA DEPORTATION COST U.S.

TAXPAYER MILLIONS OF DOLLARS A YEAR, BU IMMIGRANTS WHO ARE LATERALLY DEPORTED ARE JUST AS LIKELY TO TRY TO RETURN TO THE U.S THAT WAS CERTAINLY THE CASE FO ALFONSO, WHO TOOK THE FIRST BU OUT OF TOWN AND REJOINED ISAAC FOR ANOTHER TRY.

>> HE SAID, "COME WITH ME!

IT WON'T BE BAD, LET'S GO!

SO I SAID, "FINE, LET'S GO THEN."

>> Reporter: AND SO ALONG WITH 21 OTHER MIGRANTS THEY BEGIN THEIR FOURTH EFFORT TO ENTER THE U.S.

ACCOMPANYING THEM IS A GUIDE, COYOTE, PAID TO LEAD THE THROUGH THE ARIZONA DESERT O WHAT HE TELLS THEM WILL BE A ONE DAY, ONE NIGHT WALK.

>> Translator: WE BROUGHT TUNA WE BROUGHT CRACKERS, WE BROUGHT BREAD THINGS TO EAT, APPLES.

AND WATER, WATER MORE THAN ANYTHING ELSE.

>> Reporter: THERE IS NO BORDE FENCE HERE, BECAUSE THE AMERICAN SIDE IS OWNED BY THE TOHON O'ODHAM NATION, IT'S A NATIV AMERICAN RESERVATION AND SOON THE MIGRANTS CROSS TH BORDER HOURS INTO THEIR TRIP, THEIR GUIDE TELLS THEM AN AWFUL TRUTH, THEIR WALK IS NOT ONE TO TWO DAYS AS PROMISED, BUT FOUR O FIVE DAYS.

>> AND THAT'S WHEN I SAID TO ALFONSO, DO YOU SEE THAT THE LIED TO US IT IS A LOT OF TIME.

>> Reporter: THE NEXT DAY THEY CLIMB IN MOUNTAINOUS COUNTRY AT 3:30 IN THE AFTERNOON, THEY ENTER A BROAD, HOT VALLEY.

AND ALFONSO IS STRUGGLING.

THE TEMPERATURE, 115 DEGREES >> Translator: HE SAID, I FEEL ILL. AND AFTER ABOUT FIVE MINUTES H STARTED TO FEEL WORSE.

AND HE STARTED TO PRAY TO GO THAT HE DIDN'T WANT TO DIE, AN HE LOVED HIS CHILDREN, AND H LOVED HIS FAMILY, AND HE JUS STARTED TO GO CRAZY, WRITHIN AND SHOUTING >> Reporter: ALFONSO IS IN THE GRIPS OF HEAT STROKE HE BEGINS CONVULSING S VIOLENTLY ISAAC HAS TO HOLD HI TO KEEP HIM FROM HURTING HIMSELF.

DURING THE STRUGGLE, THE GUIDE RETURNS, TAKES ALL OF THEIR FOOD AND MOST OF THEIR WATER AND THEN ABANDONS THEM.

SO YOU'RE BOTH BEING LEFT TO DIE.

>> UH-HUH, SI.

>> Reporter: ALFONSO MAY NOT HAVE HAD TO BE IN THIS SITUATION AT ALL BEFORE HE WAS DEPORTED, HE TOL HIS WIFE IMMIGRATION AGENTS HA PRESSURED HIM TO WAIVE HIS RIGHT TO AN IMMIGRATION HEARING, A HEARING THAT MIGHT HAVE RESULTED IN HIM BEING ALLOWED TO STAY I THE U.S. TO SUPPORT HIS FIVE DEPENDENT CHILDREN >> Translator: THEY SCARED HIM THEY SAID THAT IF HE DIDN' SIGN, THEY WOULD KEEP HIM THER FOR A LONG TIME.

>> Reporter: AS STRANGE AS THA SOUNDS, THE ARIZONA STUDY SAYS THAT 28% OF DEPORTEE INTERVIEWED ALSO FELT FORCED O PRESSURED TO SIGN AWAY THEIR RIGHTS TWO HOURS AFTER ALFONSO FALL ILL, ISAAC BUILDS A LARGE SIGNAL FIRE TO ATTRACT THE BORDER PATROL, SO ALFONSO CAN BE SAVED, BUT NO LUCK.

>> I THOUGHT ABOUT STAYING THERE WITH HIM UNTIL SUNRISE, BUT SAID TO MYSELF, I HAVE TO LOOK FOR HELP >> Reporter: HE CLIMBS THE NEAREST RIDGE HOPING TO GET CELL SIGNAL ON ALFONSO'S PHONE >> Translator: I TURNED IT O AND I IMPLORD GOD, I SAID, M GOD, HELP HIM.

>> Reporter: HE MIRACULOUSLY GETS A SIGNAL.

SOON AFTER, TWO BORDER PATRO OFFICERS ARRIVE IN A TRUCK ISAAC SAYS HE TELLS THEM THE MUST QUICKLY GO TOGETHER T RESCUE ALFONSO, AND TELLS THEM EXACTLY WHERE HE IS.

INSTEAD, THEY ARREST HIM AND IMMEDIATELY TAKE ISAAC T DETENTION, ASSURING HIM THAT OTHER AGENTS WERE SEARCHING FO ALFONSO AND WOULD RESCUE HIM THAD BINGEL, THE FORMER CHIEF OF STAFF OF CUSTOMS AND BORDE PROTECTION, SAYS THAT IF ISAAC'S STORY IS TRUE, THE AGENTS DI NOT ACT PROPERLY >> IT'D BE VERY UNUSUAL IF THE THOUGHT THE PERSON WITH THEM WAS TRYING TO HELP THEM IDENTIFY A LOCATION THAT THEY WOULDN'T TAKE ADVANTAGE OF THAT INFORMATION.

THAT WOULD NOT BE NORMAL PROTOCOL >> Reporter: TWO AND A HALF DAYS AFTER ALFONSO GOT SICK, ISAAC IS DEPORTED TO MEXICO HE IMMEDIATELY CALLS ALFONSO'S FAMILY >> IN MY HEAD I THOUGHT, OKAY, IT'S SATURDAY NIGHT, SUNDAY, MONDAY, TUESDAY, IF HE MANAGED TO FIND A TREE, STAY UNDER THE TREE, AND IF HE HAD A LITTLE BIT OF WATER, HE COULD HAVE STAYED ALIVE THERE.

>> Reporter: ALFONSO'S DAUGHTE GLADYS, AN AMERICAN CITIZEN, MAKES DOZENS OF FRANTIC PHON CALLS TO THE BORDER PATROL I ARIZONA ASKING IF HER FATHER I DETAINED OR IN THE HOSPITAL?

SHE SAYS THE BORDER PATROL GIVES HER NO ANSWERS HOW LONG WAS IT UNTIL SOMEBODY SAID, "OKAY, HERE'S EXACTLY WH YOU NEED TO CALL, MAYBE THEY CAN HELP"?

>> THEY DIDN'T SAY THAT.

THEY DIDN'T SAY THAT I -- I KEPT ON RESEARCHING O THE INTERNET TILL I FOUN BORSTAR.

>> Reporter: BORSTAR, THE BORDER PATROL'S SEARCH, TRAUMA AN RESCUE UNIT.

>> THIS IS THE PART OF U.S. CUSTOMS AND BORDE PROTECTION'S MISSION THAT RARELY MAKES HEADLINES.

RESCUING THOSE IN TROUBLE ALON OUR SOUTHERN BORDER.

>> Reporter: ITS MISSION, TO PROVIDE LIFE SAVING AID" TO TH "DISTRESSED MIGRANTS ALONG THE BORDER >> IT'S PRETTY RARE FOR A LA ENFORCEMENT AGENCY TO BASICALL CREATE A RESCUE UNIT JUST TO DEAL WITH PEOPLE WHO ARE BASICALLY ENGAGED IN ILLEGAL ACTIVITY, CROSSING THE BORDER IN A HUMANITARIAN WAY >> Reporter: SO GLADYS CALLS BORSTAR, AND TELLS THEM HE FATHER IS DYING IN THE DESERT.

BUT GLADYS SAYS WHEN SHE CALLED, SHE WAS PUT ON HOLD, TRANSFERRED, OR TOLD TO TALK T SOMEONE ELSE FINALLY, 4 1/2 DAY AFTER ALFONSO FELL ILL, TH BORDER PATROL MEETS ISAAC AT THE BORDER AND TAKES HIM TO RESCUE HIS FRIEND IN THE DESERT ONCE THEY ARRIVE IN THE AREA AND START WALKING, IT TAKES JUST 4 MINUTES TO LOCATE ALFONSO.

>> IT WAS THE HARDEST THING FO ME BECAUSE OF HOW I LEFT HIM AND HOW I FOUND HIM.

>> Reporter: ALFONSO WAS LATER IDENTIFIED BY HIS DENTAL RECORDS AND PERSONAL ITEMS HIS JACKET, WATCH, KEY CHAIN AUM WOUND UP AS EXHIBITS IN THAT PIMA COUNTRY MORGUE HIS BODY WAS FOUND EXACTLY WHERE ISAAC HAD LEFT HIM, EXACTL WHERE HE SAYS HE HAD TOLD BORDER PATROL AGENTS ALMOST FIVE DAYS EARLIER TO SEARCH FOR HIM.

>> I HAVE THE TOUGHEST QUESTIO FOR YOU.

DO YOU EVER THINK ABOUT THOS LAST HOURS OF WHAT MUST HAVE BEEN GOING THROUGH HIS MIND?

>> EVERY DAY I THINK ABOUT IT EVERY DAY >> Reporter: WHAT DO YOU THINK HE WAS THINKING?

>> BECAUSE THE LAST THING -- ISAAC CALLED US AND HE TOLD US WHEN YOUR DAD WAS DYING THE ONLY THING HE WAS SAYING WAS, " DON'T WANT TO DIE.

I DON'T WANT TO DIE.

I WANT TO GET BACK TO MY KIDS.

I WANNA MAKE IT WITH MY KIDS I HAVE TO MAKE IT WITH MY KIDS I NEED TO GET BACK."

AND I JUST IMAGINE HIM ALL B HIMSELF IN THE FREAKING DESERT JUST LAYING THERE.

>> Reporter: ISAAC SAYS HE'S CONVINCED THAT BORDER PATROL NEVER BOTHERED LOOKING FOR ALFONSO THAT FIRST NIGHT, OR EVER THEY MIGHT SAY, "LISTEN, IT'S HUGE DESERT.

IT WAS IN THE MIDDLE OF TH NIGHT.

WE WERE LOOKING FOR HIM.

BUT WE JUST DIDN'T FIND HIM.

>> Translator: NO, THE TROOU, THINK, IS THAT THEY DIDN'T LOO FOR HIM.

I THINK THEY JUST LEFT HIM THERE.

>> Reporter: AND WHAT ABOUT AL THE PEOPLE IN THE UNITED STATE WHO WOULD SAY, IF YOU AN ALFONSO HAD JUST STAYED IN MEXICO, HE'D STILL BE ALIV TONIGHT.

>> Translator: WE CAME TO WORK WE DIDN'T COME TO TAKE ANYTHING.

WE CAME TO STRUGGLE TO MAKE LIFE >> Reporter: WE ASKED THE BORDER PATROL WHAT HAPPENED THAT NIGHT, FOR TAPES OF ISAAC'S 911 CALL, FOR ANY DETAILS OF THEIR SEARC FOR ALFONSO.

THEY HAVE, SO FAR, OFFERED N INFORMATION.

BUT THAD BINGEL SAYS THAT BORDER PATROL IS NOT RESPONSIBLE FO ALFONSO'S DEATH AND OTHERS LIK HIS.

>> I PUT THE BLAME FOR PUTTING PEOPLE AT RISK OF DEATH LARGEL ON THE CRIMINAL ORGANIZATIONS ON ON THE CRIMINAL ORGANIZATIONS ON THE SOUTH SIDE WHO ARE DECEIVING PEOPLE INTO THINKING OH, YOU JUST HAVE TO WALK, YOU KNOW, A COUPLE MILES AND YOU'LL HIT TH ROAD WHEN REALLY THEY'RE TALKING 20 MILES OR MORE IN REALLY REALLY HOSTILE CONDITIONS.

>> Reporter: ALFONSO'S FAMIL GATHERED AT HIS GRAVE LAST MONTH FOR THE ONE YEAR ANNIVERSARY O HIS DEATH.

HIS 15 YEAR-OLD SON IS HAVIN PERHAPS THE MOST DIFFICULT TIME, AND HAS TAKEN TO PUNCHING HOLE IN WALLS OF THE FAMILIES APARTMENT.

>> I JUST WANTED TO SAY GOOD-BYE SOMETHING, I COULDN'T.

>> Reporter: IN THE END, ONE FATHER, WHO MIGHT HAVE HAD A PATHWAY TO AMERICAN CITIZENSHIP, IS NOW DEAD.

THE OTHER CROSSED ILLEGALLY INTO THE UNITED STATES A FIFTH TIME REJOINED HIS CHILDREN, AND NOW LABORS AS A CALIFORNIA FARMWORKER, AS HE HAS FO DECADES.

YOU GET THE SENSE FO THESE TWO AND THOUSANDS LIKE THEM, NO WALL WOULD HAVE BEE HIGH ENOUGH, NO DESERT TOO FORBIDDING >> IT DOESN'T MATTER THE DANGERS THAT THEY'RE WILLING TO FACE THE DANGERS JUST TO BE WITH THEI FAMILY, BECAUSE NOTHING TO HIM WAS MORE IMPORTANT THAN BEIN WITH US.

>>> THIS "NEED TO KNOW'.

IMPORTANT THAN BEING WITH US >> Reporter: THAT'S IT FOR THI EDITION OF "NEED TO KNOW."

I'M JEFF GREENFIELD.

THANKS FOR WATCHING.