The defendants, all U.S. citizens, were convicted of conspiracy to harbor and transport illegal immigrants, as well as other counts, and all face life in prison.
Beyond conspiracy, the jurors had to decide whether each defendant was responsible for the smuggling of each immigrant involved.
They found Victor Sanchez Rodriguez, 58, guilty of eight counts of harboring and nine counts of transporting illegal immigrants; his wife, Emma Sapata Rodriguez, 59, guilty of eight counts of harboring and six counts of transporting; and her half-sister, Rosa Sarrata Gonzalez, guilty of one count of harboring.
More than 70 illegal immigrants had crowded into the back of the tractor-trailer rig to be hauled from South Texas to Houston in May 2003. As they traveled, they began to succumb to the rising heat inside the airtight trailer.
Seventeen people were dead by the time the trailer was discovered, and two others died later, all of dehydration, overheating and suffocation.
Authorities have said the temperature in the trailer reached 173 degrees. Survivors testified that the immigrants took off their sweat-drenched clothes for relief and crowded around holes they punched in the truck so they could breathe. They also kicked out a signal light to try to get the attention of passing motorists.
They were found after the driver abandoned the trailer at a truck stop in Victoria, about 100 miles southwest of Houston.
In closing arguments of the two-week trial, prosecutors had asked jurors to remember the victims.
"It's time to send a message to these three (smugglers) that their days of making money on the pain, desperation of others has come to an end," Assistant U.S. Attorney Daniel Rodriguez said Friday.
Defense attorneys had argued that their clients were bit players in a scheme orchestrated by others.
Karla Patricia Chavez, the alleged leader of the smuggling ring, testified that another member, Abelardo Flores, had sent the trailer toward Houston when the original destination was near Corpus Christi, which would have been a shorter trip. Flores has pleaded guilty and cooperated with prosecutors.
In all, 14 people were indicted in the case.
Two, including a son of Sanchez and Sapata, were convicted of various smuggling charges. Charges against two were dismissed, five others previously pleaded guilty and one man remains a fugitive.
The truck's driver, Tyrone Williams, the only one to face the death penalty in the case, was convicted in March of transporting illegal immigrants. Prosecutors want to retry Williams, a Jamaican citizen who lived in Schenectady, N.Y., on other counts that could bring the death penalty. An appeal is pending.
The three defendants convicted Wednesday originally were charged with 58 counts of harboring and transporting illegal immigrants, but U.S. District Judge Vanessa Gilmore had dismissed most of the counts, citing lack of evidence.
The jurors deliberated for more than 13 hours over four days, and at one point told the judge they were deadlocked, before reaching a verdict Wednesday morning.