(CNN) -- An Arizona couple who wanted to adopt a woman's baby know more than they're saying about the 8-month-old boy's disappearance, police say. 

Gabriel Johnson hasn't been seen since December 26, police said, and his mother was arrested last week in Miami Beach, Florida, after not reporting for a December 28 child custody hearing in Arizona. 

"We have some good indications at this point with our investigation that Tammi and Jack Smith do know more information than they have provided to us that could possibly lead us to Gabriel," Sgt. Steve Carbajal, spokesman for the Tempe (Arizona) Police Department, told HLN's Nancy Grace on Thursday. 

For their part, the Smiths told HLN's Jean Casarez on "Nancy Grace" that they voluntarily took polygraph tests Friday at the Tempe Police Department. 

"The polygraph test is not like what you see on TV," Jack Smith said. "It's almost like being strapped into the electric chair, so it's very intensive. And we were very happy to do it." 

The Smiths have said they met Elizabeth Johnson, 23, seven months ago during a long layover at an airport, and later the three discussed a plan to adopt Johnson's child, Gabriel. 

But the boy's father, Logan McQueary, has legal custody and has said Elizabeth Johnson urged him to sign papers giving the Smiths custody of the boy, but he refused. 

"She didn't want Logan to have the baby, and we couldn't adopt the baby because Logan wouldn't sign the papers," Tammi Smith said on "Nancy Grace." 
What did the AZ couple want to do?
how old?
what happened?
name of baby?
date last seen?
Moms name?
age?
Where was mom arrested?
when was court date?
who is steve carbajal?
Did they go on TV?
What station?
What show?
Did boy have a dad?
name?
did he have custody?
Did the anyone take a polygraph test?
who?
was it easy?
were they happy to do it?
Did they pass the test?
adopt a baby
 An Arizona couple who wanted to adopt a woman's baby know more than they're saying about the 8-month-old boy's disappearance, police say. 

8 months
An Arizona couple who wanted to adopt a woman's baby know more than they're saying about the 8-month-old boy's disappearance, police say. 

the baby disappeared
Gabriel Johnson hasn't been seen since December 26, police said, and his mother was arrested last week in Miami Beach, Florida, after not reporting for a December 28 child custody hearing in Arizona. 

Gabriel Johnson
Gabriel Johnson hasn't been seen since December 26, police said, and his mother was arrested
December 26
Gabriel Johnson hasn't been seen since December 26, police said
Elizabeth Johnson,
The Smiths have said they met Elizabeth Johnson, 23, seven months ago during a long layover at an airport, and later the three discussed a plan to adopt Johnson's child, Gabriel. 

23
The Smiths have said they met Elizabeth Johnson, 23, seven months ago 
Miami Beach, Florida,
 his mother was arrested last week in Miami Beach, Florida,
December 28
r a December 28 child custody hearing in Arizona. 
Tempe police sargeant
 Sgt. Steve Carbajal, spokesman for the Tempe (Arizona) Police Department, told HLN's Nancy Grace on Thursday. 

yes
Steve Carbajal, spokesman for the Tempe (Arizona) Police Department, told HLN's Nancy Grace on Thursday.
HLN
For their part, the Smiths told HLN's Jean Casarez on "Nancy Grace" that they voluntarily took polygraph tests Friday at the Tempe Police Department. 

Nancy Grace
For their part, the Smiths told HLN's Jean Casarez on "Nancy Grace" that they voluntarily took polygraph tests Friday at the Tempe Police Department. 
yes
But the boy's father, Logan McQueary, has legal custody and has said Elizabeth Johnson urged him to sign papers giving the Smiths custody of the boy, but he refused. 

Logan McQueary
But the boy's father, Logan McQueary, has legal custody and has said Elizabeth Johnson urged him to sign papers giving the Smiths custody of the boy, but he refused. 

yes
But the boy's father, Logan McQueary, has legal custody 
yes

For their part, the Smiths told HLN's Jean Casarez on "Nancy Grace" that they voluntarily took polygraph tests Friday at the Tempe Police Department. 

the Smiths
For their part, the Smiths told HLN's Jean Casarez on "Nancy Grace" that they voluntarily took polygraph tests Friday at the Tempe Police Department. 

no
"The polygraph test is not like what you see on TV," Jack Smith said. "It's almost like being strapped into the electric chair, so it's very intensive. And we were very happy to do it." 
yes
"The polygraph test is not like what you see on TV," Jack Smith said. "It's almost like being strapped into the electric chair, so it's very intensive. And we were very happy to do it." 

unknown
unknown